program report for 1998

Irrigated rice ecosystem 3

Research programsIrrigated rice ecosystem

BREEDING TO BREAK YIELD CEILINGS:A SYSTEMS APPROACH 4Radiation use efficiency in rice (APPA) 4Peculiar growth patterns on route to high yields

(APPA) 6Progress in increasing grain yield by breeding a new

plant type (APPA, PBGB) 7Hybrid rice 9

Hybrid rice network (PBGB) 9Release of IRRI hybrids (PBGB) 9Elite rice hybrids (PBGB) 9New cytoplasmic male sterile (CMS) lines

(PBGB) 11Development of thermosensitive genic male sterile

(TGMS) lines (PBGB) 11IR lines named as varieties (PBGB) 11

Importance of nitrate vs ammonium for potential yield(SWS) 12

Identifying new genes with durable resistance to tungroviruses (EPP) 13

Development of rice blast-resistant monogenic lines(PBGB) 13

SUSTAINING SOIL QUALITY IN INTENSIVE RICESYSTEMS 15Variability of optimal nitrogen applications for rice 15

Optimal N rates (SWS, SS) 15Spatial variability at the same site (SWS, SS) 16

Internal nutrient efficiencies in irrigatedlowland rice 17

Current situation in farmers’ fields (SWS) 17Modeling the nutritional balance (SWS) 17Case study: Maligaya, Central Luzon,

Philippines (SWS) 19

INCREASING WATER USE EFFICIENCY IN RICECULTURE 20Management of cracked soils for water saving during

land preparation (SWS) 20Population dynamics of Echinochloa crus-galli in wet-

seed rice (APPA) 22Semidry rice production for irrigation water savings

(SWS) 24

IMPROVING PEST MANAGEMENT 26Motivating farmers to test pest management changes

through use of printed materials and radio (EPP) 26Testing the validity of surrogate taxa for canopy and

floodwater invertebrates (EPP) 26Directional movement of predators between the

irrigated rice field and its surroundings (EPP) 27Seed health evaluation for farmer rice crop management

(EPP) 28

COPING WITH GLOBAL CLIMATE CHANGE:REDUCING METHANE EMISSION FROM RICEFIELDS (SWS) 28

IRRIGATED RICE RESEARCH CONSORTIUM 29

PROGRESS OF UNREPORTED PROJECT 30Improving the productivity and sustainability of rice-

wheat systems (SWS, APPA, EPP) 30

PROGRAM OUTLOOK 30

4 IRRI program report for 1998

Irrigated rice ecosystem

Rice production must be increased by 70% over thenext three decades to meet growing demand for foodand to sustain the global food security. For theforeseeable future, the bulk of that demand willcontinue to be met by intensive irrigated rice systems.Because of limited opportunities for expansion of rice-growing areas plus increased urbanization to furtherreduce rice areas, reduced labor available for agricul-ture due to its shifting to nonagricultural sectors, andincreased scarcity of water resources, it is essentialto increase rice productivity per unit of area, per unitof labor, and per unit of input to meet the projectedgrowth in demand.

The irrigated rice ecosystem research is premisedon increasing rice production through 1) shifting theyield frontier upward, 2) increasing the efficiency ofcrop production inputs, 3) sustaining the rice base forirrigated lowlands, and 4) minimizing the effects of theglobal climate change on the external environment.

Breeding to break yield ceilings:a systems approach

Radiation use efficiency in riceJ. Sheehy, J. Dionora, A. Ferrer, and R. Torres

The physical limits to rice yield are ultimately setby the absorption and conversion of light and themaximum diffusion rate of CO2. Two approacheswere taken to answer the question whether a ther-modynamic barrier prevents increases in yield be-yond 10 t ha-1.

● The concept of radiation conversion tobiomass in rice was examined theoreticallyand experimentally.

● Estimates of the conversion obtainedthroughout a growth cycle in irrigated ricegrowing in the dry season (DS) with abundantfertilizer were compared.

A general equation for a rice crop can be devel-oped over the growing season from transplanting(tr) to maturity (tm) so that

(1)

where Y is the yield of required parts of the plant (gm-2); H is the fraction of crop dry matter (DM) thatbecomes the yield, i.e., the harvest index; ε is theradiation conversion factor (g DM MJ-1), t is time,tr is date of transplanting, and tm is time of matu-rity; Q(t) is photosynthetically active radiation(PAR) incident on the crop as a total (MJ m-2); andf(t) is the fraction of radiation intercepted at time t(dimensionless). In high-yielding rice, H is about0.5.

The instantaneous value of radiation use effi-ciency, (E(t)) expressed as a percentage at time t,can be written

Y = Hε ∫tm (Q(t) f(t))dttr


E(t) = 100 φ (2)dW/dtIa(t)

where φ is the energy content of the biomass (J g-1);W is the weight of the total crop biomass (g m-2), tis time, and Ia(t) is the solar energy (MJ m-2 PAR)absorbed by the canopy and is the difference be-tween incident and transmitted plus reflected PAR.It should be noted that when the factors 100 and φare omitted, the radiation conversion factor(RCF)(ε(t)) is estimated and has units such as gMJ-1. After much simplification, the RCF can be es-timated for the crop when it is vegetative, and lossesfrom death and detachment are negligible, and writ-ten as

where Pg is the daily total gross photosynthesis (gCH2O m-2 d-1), ma is the value of the maintenancecoefficient at the average temperature for the day,WT is the total biomass, and Itotal is the daily total ofintercepted PAR (MJ m-2 d-1). These values can allbe calculated from a combination of published andexperimental data.

The variation in the RCF caused by changes inincident PAR (Fig. 1) was examined using equation(3) for the conditions shown in Table 1. The rela-tionship highlighted two interesting features. Thefirst was that RCF varied markedly with PAR. Itincreased from a negative value to a maximum, 3.84

εdmean = (3)0.75Pg – maWT

Itotal

g total DM MJ-1 and then declined again. It wasnegative at low values of PAR, when maintenancerespiration was greater than the difference betweengross photosynthesis and synthetic respiration. Thesecond decline was caused by the decrease in theefficiency of canopy photosynthesis with increasingirradiation.

An experiment with IR72 was conducted at IRRIin 1997 DS. The crop was transplanted at the stand-ard spacing of 20 × 20 cm and irrigated. It had highapplications of N (480 kg N ha-1), and insecticidesapplied to control insect pests. Panicle initiation oc-curred at 43 d after transplanting (DAT). Anthesisstarted at 61 DAT and finished between 75 and 82DAT. The final grain harvest was taken at 102DAT. Measurements were made immediately be-fore each harvest of instantaneous incident PARabove the canopy and transmitted PAR below thecanopy. The fraction intercepted was computedfrom these results and an average for the period wasobtained by interpolation. The amount of PAR(daily total) incident on the site was taken fromrecords at the IRRI meteorological station. PARwas assumed to be 50% of solar radiation.

There are two sets of values of DM with whichto compute the RCF: the actual values measured onthe harvest dates and the values obtained for theharvest dates after fitting a polynomial curve (r2 >0.95). The RCF was computed using the mean in-tercepted PAR for the interval up to the harvest date.Figure 2 shows that variation in consecutive meas-ures of the biomass gave rise to considerable varia-tion in the estimated values of the RCF. Valuesranged from -17 to 21 g DM MJ-1 and the overallaverage was 2.5 g DM MJ-1. The value of the RCFwas highly sensitive to errors in both biomass andintercepted PAR. The RCF calculated for the fittedvalues of biomass (Fig. 2) shows a much smoother

Table 1. Values of crop and weather variables used in ra-diation use efficiency calculations. IRRI, 1998.

Variable or parameter Value Units

Leaf area index 1.12 m2 leaf m-2 groundTotal biomass including roots 1.2 t ha-1

Maintenance respiration coefficient at 20 oC 0.015 g CH2O g-1 DM d-1

Av daily temperature 23.5 (21-26) oCExtinction coefficient 0.45 dimensionlessDaylength 11.7 hLeaf photosynthesis 36 µmol CO2 m

-2 s-1

1. The variation in the radiation conversion factor (shoot+root/PAR) with a range of incident PAR recorded at IRRI. Calculatedfor a young rice crop from the values recorded in Table 1. IRRI,1998.

4

2

0

-2

-40 5 10 15

Radiation conversion factor (g DM MJ-1)

Incident PAR (MJ m-2 d-1)


pattern but still varies during the season. The over-all average using this approach was 3.7 g DM MJ-1.Both of the estimates of the RCF suggest a declineduring anthesis and an increase during grain filling.The grain yield in this experiment was 11.63 ± 0.67t ha-1, suggesting a value for the RCF close to 2.6 gDM MJ-1. The traditional method of plottingbiomass at each harvest against accumulated inter-cepted PAR and fitting regression through the ori-gin gave a value of 2.5 DM MJ-1.

The results suggest that the value of the RCF var-ies because of changes in daily irradiation. The RCFdeclines at high irradiation even though the canopyis increasing its rate of carbon capture and potentialgrowth rate. Even the method used to calculate theRCF can influence its estimated mean value. Errorsof measurement in particular have a strong influ-ence (Fig. 2). It seems likely that the high N nutri-tion of this experimental crop enabled it to makebetter use of intercepted PAR. We suggest a valuefor the RCF close to 2.6 g DM MJ-1 (shoot/PAR) forrice grown with high levels of N when yields be-yond 12 t ha-1 are attainable.

Peculiar growth patterns on route to highyieldsFor 30 yr, 10 t ha-1 has remained the maximumvalue regarded as a thermodynamic yield barrier inthe tropics. We demonstrated that the yield barriercan be exceeded when sufficient N was given tomaintain the critical concentration for metabolic

activity, and that the highly productive crop showedan unusual growth pattern.

Crops of the elite indica-type rice cultivar IR72and current lines of the new plant type (NPT) weretransplanted and irrigated with standard treatmentduring 1997 DS. Weekly applications of N fertilizertotaled 420 kg N ha-1. Strings across some plots pre-vented lodging in IR72. Yields of both IR72 and theNPT were 11.6 t ha-1. The NPT was damaged dur-ing grain filling by the striped stem borer. The har-vest index (grain dry matter as a fraction ofaboveground DM) was 0.55 for IR72 and 0.40 forNPT.

In contrast to the usual logistic curve exhibitedby annual crops, we found an apparent plateauaround the time of flowering (Fig. 3a and 3b). Har-vest of aboveground biomass was every 2 d fromthe start of flowering and it was that frequency ofsampling which revealed the plateau. The growthanomaly could be the slowing of growth duringflowering, deviation from expected curve A, or veryrapid growth afterwards, deviation from curve B(Fig. 3c). If harvests had been sampled every 1 or 2wk, as commonly practiced, a standard logistic-typecurve would have appeared acceptable (Fig. 3d).

Changes in incident solar radiation and the frac-tion intercepted by the crops from the start of flow-ering were too small and inconsistent to account forthe slowing of growth. Other possible explanationsfor slow growth, such as movement of DM betweenroots and shoots, loss of weight due to pollen shed,

2. The RCF (shoot/PAR) calculated at intervals during the growth of a rice crop using the measured shoot biomass(--o--) and for the same periods the shoot biomass obtained from a curve fitted to measured biomass ( ). IRRI, 1998.

-20

-15

-10

-5

0

5

10

15

20

25Radiation conversion factor (g DM MJ-1)

0 20 40 60 80 100

Days after transplanting


and loss of weight from decay of dead plant matter,did not seem to account for the size of the phenom-enon.

If the results are interpreted as a marked upswingin growth after flowering, an alternative explanationis required. The imposed critical N managementenabled these crops to sustain two or three liveleaves per tiller through to final harvest, a timewhen most leaves are usually dead. Consequently,we calculated (with the model Oryza1) that grainfilling declined by only about 50% during photo-synthesis, whereas it is reported that respiration de-creased ninefold over the same period. The differ-ence between the rates of the two processes wouldprovide the resources for the late surge in growth.

Our inability to explain the anomalous growthpattern suggests that we do not yet have a completeunderstanding of the physiology of high-yieldingcrops.

Progress in increasing grain yield by breedinga new plant typeS. Peng, G. Khush, R. Visperas,and A. Evangelista

Breeding of the NPT with large panicles and lowtillering aimed to break the yield barrier of 10 t ha-1

in the tropics. However, field tests at several sitesbetween 1994 and 1997 indicated low yields fromNPT lines due to poor grain filling and low biomassproduction. The design of the NPT was slightlymodified by moderately increasing tillering capac-ity, plant height, and growth duration, and slightlydecreasing panicle size. In 1998 DS and WS, weevaluated recently developed NPT lines at IRRI todetermine if potential grain had increased.

Forty-three lines were grown in DS and 51 lineswere grown in WS. IR72 was the check variety. In1998 DS, 22-d-old seedlings were transplanted on

3. The growth of aboveground biomass (points) of productive rice crops grown in DS at IRRI: (a) the cultivar IR72, (b) the new planttype, (c) as in (a) with logistic curves A and B, and (d) a logistic through data representing weekly sampling. The growth curves for1997 are backtransformed from cubic polynomials, chosen for parsimony and interpretability of the coefficients, fitted to the naturallogarithm of aboveground dry weight, to make variances more homogeneous. The period of flowering is shown for each crop. In (c),the pecked lines are the expected near logistic curves with early exponential growth then linear growth before leveling off towardmaturity. IRRI, 1998.

25

20

15

10

5

0

30

25

20

15

10

5

0

25

20

15

10

5

0

25

20

15

10

5

0120100806040200 100806040200

100806040200100806040200

Aboveground biomass (t ha-1)

a

b

c

d

Fstart Fend

Fstart Fend

SigmoidGaussian

Days after transplanting


7 Jan. Fertilizer N was applied at 120 kg ha-1. In1998 WS, transplanting was on 25 Jun with 22-d-old seedlings. Fertilizer N input was 100 kg ha-1.Hill spacing was 0.10 × 0.15 m, with one seedlingper hill in both seasons. Samples were taken from a0.5-m2 area at maturity to determine paniclenumber, spikelets per panicle, grain-filling percent-age, and 1,000-grain weight. Grain yield was deter-

mined from a 5-m2 area and adjusted to a moisturecontent of 0.14 g H2O g-1 fresh weight.

Seven NPT lines produced greater or the sameyield as IR72 in 1998 DS (Table 2). All of those hada panicle size of 150-200 spikelets panicle-1, whichmay be the optimal range of panicle size for theNPT. High-yielding NPT lines had large spikeletnumber m-2, or high grain-filling percentage, or

Table 2. Grain yield and yield components of 43 new plant type (NPT) lines and IR72. IRRI, 1998 DS.

Grain Panicles Spikelets Spikelets Filled 1,000-NPT line yield m-2 panicle-1 m-2 spikelets grain

(t ha-1) (no.) (no.) (no. × 103) (%) weight (g)

IR70554-48-1-2 8.84 229 161 36.9 71.6 29.2IR65564-44-2-2 8.59 216 186 40.1 72.7 25.1IR69093-41-2-3-2 8.45 222 186 41.2 77.8 23.3IR68552-100-1-2-2 8.38 234 166 38.9 84.2 24.9IR69853-70-3-1-1 8.27 219 195 42.7 65.7 24.8IR70479-45-2-3 8.19 259 199 51.5 57.2 22.3IR66738-118-1-2 8.18 232 183 42.6 59.1 25.1IR72a 8.07 532 90 47.8 80.9 21.4IR69137-34-1-3-1 8.04 280 136 38.0 71.8 25.4IR67962-84-2-2 8.00 250 177 44.2 60.6 23.3IR67966-188-2-2-1 7.90 239 211 50.4 52.0 25.1IR68011-15-1-1 7.90 263 142 37.1 72.3 24.7IR69116-67-3-2-3 7.89 220 170 37.3 78.7 25.5IR68552-55-3-2 7.86 279 153 42.9 84.0 21.4IR65564-44-5-1 7.83 224 150 33.7 77.9 24.5IR68544-29-2-1-3-1-2 7.80 239 167 39.8 76.8 26.4IR69923-31-3-2-3 7.58 313 117 36.7 78.6 24.0IR65600-87-2-2-3 7.58 279 129 35.8 57.0 32.2IR66158-38-3-2-1 7.48 215 146 31.4 80.2 29.6IR66160-121-4-4-2 7.47 309 98 30.3 90.4 25.9IR65600-54-6-3 7.46 250 126 31.3 83.1 26.0IR65564-22-2-3 7.45 263 167 43.6 59.4 26.6IR69432-54-1-1-2-2 7.44 207 170 34.8 38.3 23.9IR68019-60-3-3-2 7.43 341 114 38.9 77.7 23.7IR66160-121-4-1-1 7.40 326 95 31.0 89.4 25.5IR70491-33-2-2 7.36 221 177 39.2 57.3 26.1IR67962-40-6-3-3 7.36 242 210 50.8 45.3 24.4IR65600-42-5-2 7.28 273 121 33.1 83.1 25.8IR65600-77-4-2-1 7.27 226 143 32.3 67.7 26.8IR66160-5-2-3-2 7.26 287 135 38.9 77.4 23.1IR69092-57-3 7.25 276 177 48.8 56.6 26.1IR66160-121-4-5-3 7.25 329 96 31.6 92.5 25.0IR65600-96-1-2-2 7.24 237 140 33.1 79.0 28.9IR65600-38-1-2-1 7.22 239 154 36.7 83.6 22.0IR65598-112-2 7.08 219 184 40.0 50.6 24.5IR69800-5-3-1-2 7.01 248 130 32.2 88.4 24.9IR69132-17-2-2-2 7.00 275 132 36.2 78.9 24.1IR67962-84-2-2-2 6.97 281 154 43.2 61.4 23.9IR67966-44-2-3-2 6.91 215 197 42.1 54.9 24.2IR66750-6-2-1 6.88 229 164 37.6 53.1 24.5IR66159-189-5-5-3 6.75 274 134 36.6 82.0 23.1IR65600-129-1-1-2 6.67 200 147 29.4 82.7 27.4IR65600-27-1-2-2 6.64 245 97 23.8 84.0 33.7IR65600-127-6-2-3 6.58 191 154 29.3 82.6 25.1 LSD (0.05) 0.83 30 20 5.5 5.8 0.5

aCheck variety.


both. Four NPT lines had grain-filling percentage ofmore than 85%, significantly higher than that ofIR72. However, the high grain-filling percentagewas associated with their small number of spikeletsm-2, and grain yield of those lines was limited bysink size.

In 1998 WS, 30 NPT lines had equal or greateryield than IR72 (Table 3). IR65600-42-5-2 produced7.7 t ha-1—2.5 t ha-1 more than IR72. Many NPTlines produced significantly more spikelets m-2 be-cause of their larger panicle size compared with thatof IR72. Nine NPT lines had grain-filling percent-age higher than 70% compared with 65% from IR72.Most NPT lines had greater grain weight than IR72in both seasons.

These results indicate significant progress in im-proving the NPT. The improvement was mainly re-flected by the increase in grain-filling percentage.

Hybrid riceS. Virmani, R. Toledo, C. Casal, R. Ona, andD. Sanchez

The goal of hybrid rice research at IRRI is to in-crease rice yields beyond the level of high-yieldingsemidwarf rice varieties by exploiting the phenom-enon of hybrid vigor.

During 1998, 386 elite inbred lines were testedfor their ability to maintain sterility or restore fertil-ity of three cytoplasmic male sterility (CMS) sys-tems—CMS WA, CMS-ARC, CMS-mutagenizedIR62829B—used in the breeding program. In all1,001 testcrosses were evaluated and 192 newbackcrosses were initiated to develop new CMSlines in BC1 to BC6 generations. Seeds of 645 hy-brids were produced and 780 hybrids were evalu-ated in observation yield trials (495), preliminaryyield trials (214), and advanced yield trials (71). Fif-teen hybrids were nominated for national trials bythe Philippine Rice Research Institute (PhilRice).Thirty-one hybrids were nominated for inclusion inInternational Rice Hybrid Observation Nursery(IRHON). Nucleus and breeder seed of 32 CMSlines and 21 restorer lines were also produced forsharing with public- and private-sector institutionsworking on hybrid rice in national programs.

HYBRID RICE NETWORK

IRRI launched a network project titled, Develop-ment and Use of Hybrid Rice Technology in Asia.Funding was provided by the Asian DevelopmentBank (ADB) and collaboration established betweenIRRI, the Food and Agriculture Organization of theUnited Nations (FAO), Asia Pacific Seed Associa-tion (APSA), and seven Asian countries—Bangla-desh, China, India, Indonesia, Philippines, SriLanka, and Vietnam. The project will expedite thedevelopment and use of hybrid rice technology inthe six countries.

Meetings of the project during 1998 establishedproject goals, objectives and expected outputs, andspecified the roles of IRRI, FAO, APSA, and theNARS. Action plans and budget of the activities tobe implemented by member countries and their par-ticipating institutions during 1998 and 1999 wereprepared and approved.

RELEASE OF IRRI HYBRIDS

The IRRI hybrid IR69690H (IR58025A/BR827-35-3-1-1-1R) was released by Maharashtra state gov-ernment in India as Karjat Rice Hybrid-1 orSahyadri. It has intermediate height (110-120 cm),medium growth duration (125-130 d), long slendergrains with slight aroma and intermediate amylose,and outyielded variety Jaya by about 30% in on-farm trials.

Four other rice hybrids released in India—CORH2 and ADRH1 in Tamil Nadu, and NarendraSankar Dhan 2 and Pant Sankar Dhan 1 in UttarPradesh—were derived from the IRRI-bred CMSline IR58025A, which indicated the direct utility ofIRRI-bred parental lines for the national programs.

ELITE RICE HYBRIDS

Sixteen rice hybrids showed at least 1 t ha-1 yieldadvantage in advanced yield trials conducted atIRRI during 1998. Five of those hybrids yieldedconsistently higher in both seasons (Table 4).


Table 3. Grain yield and yield components of 51 NPT lines and IR72. IRRI, 1998 WS.

Grain Panicles Spikelets Spikelets Filled 1,000-NPT line yield m-2 panicle-1 m-2 spikelets grain

(t ha-1) (no.) (no.) (no. × 103) (%) weight (g)

IR65600-42-5-2 7.67 327 96 31.4 74.4 22.7IR65564-44-2-3 6.90 340 110 37.5 58.5 25.6IR66160-121-4-1-1 6.40 383 86 32.5 78.3 22.2IR66158-38-3-2-1 6.39 273 139 37.9 52.0 29.2IR66160-121-4-5-3 6.26 326 112 36.9 73.3 22.5IR66160-121-4-4-2 6.24 328 91 29.6 80.6 24.5IR68552-55-3-2 6.00 280 142 39.8 66.3 21.6IR69132-17-2-2-2 5.75 259 102 26.5 74.0 25.7IR66159-189-5-5-3 5.58 293 137 40.1 49.6 22.4IR65600-27-1-2-2 5.55 280 81 22.8 71.7 31.0IR65564-44-5-1 5.54 276 119 32.9 61.1 24.1IR66160-5-2-3-2 5.50 284 129 36.5 51.5 23.6IR65600-77-4-2-1 5.48 264 131 34.6 26.1 25.6IR65600-96-1-2-2 5.43 295 123 36.3 43.9 27.2IR65564-22-2-3 5.41 302 145 43.8 38.5 24.3IR69853-70-3-1-1 5.37 209 192 40.0 37.5 22.9IR65564-22-2-3 5.35 356 91 32.3 53.4 25.5IR65600-54-6-3 5.34 288 107 30.8 68.8 24.0IR65600-87-2-2-3 5.34 275 85 23.6 53.1 33.1IR67962-84-2-2 5.26 276 172 47.3 40.0 24.1IR69800-5-3-1-2 5.25 260 123 31.8 70.9 22.9IR69923-3-1-3-2-3 5.23 271 120 32.5 60.9 21.8IR66750-6-2-1 5.21 269 133 35.6 22.4 24.0IR70559-AC5 5.19 237 140 33.3 61.4 23.0IR65600-127-6-2-3 5.19 270 141 38.0 50.0 23.6IR65600-129-1-1-2 5.13 243 125 30.5 55.2 28.0IR67966-188-2-2-1 5.12 185 122 22.4 58.3 31.7IR68544-29-2-1-3-1-2 5.11 260 95 24.7 73.9 25.9IR71204-78-3-3 5.02 218 133 28.9 45.3 27.9IR69137-34-1-3-1 5.02 302 115 34.8 57.1 25.2IR72a 5.01 469 72 33.7 65.0 20.1IR69093-41-2-3-2 4.98 219 136 29.8 62.5 22.4IR68552-100-1-2-2 4.95 230 116 26.7 70.7 27.2IR66160-5-2-3-2 4.94 310 135 41.7 42.9 23.5IR72926-AC1 4.92 229 179 40.7 32.5 25.8IR65564-22-2-3 4.88 311 105 32.5 35.2 24.7IR66738-118-1-2 4.87 266 179 47.5 20.2 25.5IR69092-57-3 4.86 247 128 31.6 57.3 27.2IR68019-60-3-3-2 4.82 331 87 28.7 55.4 25.6IR68011-15-1-1 4.76 280 108 30.4 58.8 23.7IR70491-33-2-2 4.75 230 150 34.4 35.2 25.5IR71218-5-2-1 4.74 260 152 39.3 35.0 26.2IR69116-67-3-2-3 4.68 253 151 38.4 41.0 25.4IR67962-40-6-3-3 4.59 286 139 39.8 32.2 24.5IR69432-54-1-1-2-2 4.57 228 132 30.0 12.0 23.3IR70479-45-2-3 4.50 248 201 50.0 38.0 21.9IR70554-10-3-1-3 4.45 237 157 37.1 35.2 26.3IR67966-44-2-3-2 4.44 251 129 32.6 66.8 27.8IR67962-84-2-2-2 4.27 237 132 31.2 47.9 25.4IR65598-112-2 4.12 245 133 32.5 15.3 23.8IR70554-48-1-2 4.10 268 119 31.8 33.6 27.7IR65600-38-1-2-1 3.66 247 140 34.7 47.8 20.9 LSD (0.05) 0.54 29 16 5.2 8.2 0.6

aCheck variety.


NEW CYTOPLASMIC MALE STERILE (CMS) LINES

Sixteen new CMS lines were bred possessing WA,Gambiaca, Dissi, and Kalinga cytoplasms (Table 5).In addition, we also have elite CMS lines possess-ing ARC and mutagenized IR62829B cytoplasms.Thus, the cytoplasmic base of CMS lines developedat IRRI has been reasonably diversified. The CMSline IR68897A developed in 1992 is stable for com-plete pollen sterility, has good outcrossing, and hasadaptability to tropical conditions. During 1998,many heterotic combinations were identified in ob-

servation, preliminary, and advanced yield trials.Those were derived from IR68897A, which pos-sesses long slender grains.

DEVELOPMENT OF THERMOSENSITIVE GENIC MALE

STERILE (TGMS) LINES

We evaluated 2,107 F3-F5 progenies in pedigreenursery. Among F5 progenies, 112 good lookingmale sterile plants were selected and transferred tothe phytotron to induce fertility. Fifty of those plantsreverted to partial fertility in the phytotron. Seedsproduced from them were used for evaluation ofmale sterility in the field at high temperatures(maximum temperature above 30 °C). Based ontheir good phenotypic acceptability score (1-3),good fertility reversion (score 1-5), and completemale sterility in the field (using the natural tempera-ture variation), four TGMS lines were identified forsharing with national programs: IR68492-1-6-13-B-4-8-B, IR71018-13-73-3-6-B, IR70977-16-5-4-1-12-B, and IR70978-8-22-5-14-13-B.

IR LINES NAMED AS VARIETIES

Thirteen IRRI breeding lines from the irrigatedbreeding program were named as varieties in threecountries (Table 6). This brought the number ofIRRI breeding lines named as varieties by nationalprograms to 308.

Table 5. New cytoplasmic male sterile lines developed in1998 at IRRI.

Designation Parentage Source ofcytoplasm

IR74604A IR69624A/7*BW306-2 WAIR74605A IR69628A///7*BPI76/ WA

N22//Taichung 65IR75595A D297A/7*IR68885B DissiIR75596A D297A/7*IR68897B DissiIR75597A D297A/7*IR68898B DissiIR75598A D297A/7*IR69619B DissiIR75599A D297A/7*IR69626B DissiIR75600A G46A/7*IR68889B GambiacaIR75601A G46A/7*IR68897B GambiacaIR75602A G46A/7*IR69619B GambiacaIR75603A G46A/7*IR69626B GambiacaIR75604A G46A/7*IR69624B GambiacaIR75605A IR68280A/7*IR62898-2-8-6-2 WAIR75606A IR68897A/7*IR68271-127-2-2 WAIR75607A Krishna A/7*IR69619B KalingaIR75608A Krishna A/7*IR69627B Kalinga

Table 6. Breeding lines from the irrigated breeding pro-gram named as varieties in 1998.

Breeding line Name given Countrywhere named

IR2061-213-2-17 (IR34) Mamokatra MadagascarIR2070-747-6-3-2 IR32 MaliIR2071-625-1-252(IR36) Tsy Milofika MadagascarIR8866-82-1-3-1-3 Mazana (X1228) MadagascarIR20913-B-160 Rojovo (X1289) MadagascarIR28128-45-2 Mananoro MadagascarIR21363-13-2-2 Mahadignirano MadagascarIR25579-135-3 Rojomena MadagascarIR48525-100-1-2-1 Rohat CambodiaIR49830-7-1-2-1-3 Popoul CambodiaIR56383-35-3-2-1 Chul’sa CambodiaIR57529-9-2-1-3 Baray CambodiaIR62037-71-3-1-1-3 Rumpe Cambodia

Table 4. Yield of five elite rice hybrids identified in ad-vanced yield trials. IRRI, 1998.

Yield (t ha-1)Hybrid or check variety

DS WS

IR69622A/IR29723-143-3-2-1R 9.4 5.8IR68888A/IR63875-196-2-2-1-3R 9.3 5.7IR68897A/IR65620-58-2-3-2-3R 9.0 5.4IR68897A/IR60819-34-2-1R 8.5 5.4IR68897A/IR63874-187-2-2-1-2R 8.4 4.2PSBRC 28 7.4 3.5PSBRC 18 7.4 3.6 LSD (5%) 1.0 0.8 LSD (1%) 1.3 1.0


Importance of nitrate vs ammonium forpotential yieldH. Kronzucker and G. Kirk

Growth and yield in most plant species are superiorunder mixed NO3

-–NH4+ nutrition compared with ei-

ther N source alone. However, only small concentra-tions of NO3

- are generally present in flooded ricesoils, arising as a result of nitrification of NH4

+ inaerobic zones at the soil surface and in the rhi-zosphere. Nitrate so formed may diffuse into the soilbulk and be lost through denitrification. It has, there-fore, been assumed that NO3

- uptake is not important.But although NO3

- concentrations may be small,fluxes and rates of uptake may be large if the planthas the necessary capacity for processing NO3

-.In collaboration with the University of British

Columbia, we used the short-lived tracer 13N tostudy root transmembrane fluxes and cytoplasmicpool sizes of NH4

+ and NO3- in IR72. This showed

that the capacity of rice roots for NO3- acquisition

is greater than that for NH4+. Influx of both N spe-

cies in the relevant concentration range followedMichaelis-Menten kinetics typical of high-affinitytransport systems (Fig. 4). Km values were 26 ± 5.6mM for NO3

- and 51 ± 18.4 mM for NH4+, indicat-

ing a higher affinity for NO3- than for NH4

+. Influxof NO3

- exceeded that of NH4+ by about 50% at all

concentrations examined; Vmax values were 8.1 forNO3

+ and 5.7 mmol g-1 h-1 for NH4+. Using a tech-

nique based on rates of efflux of labeled N fromroots, we quantified cytoplasmic pool sizes, half-lives of cellular exchange, and flux partitioning.Cytoplasmic NH4

+ concentrations were large (20 ±3.21 mM), but cytoplasmic NO3

- concentrationswere even larger (37 ± 4.18 mM), surpassing val-ues reported for barley.

Notwithstanding the differences in cytoplasmicconcentrations, half-lives of cellular exchange weresimilar (14 ± 0.9 min for NH4

+ and 16 ± 2.3 min forNO3

-). These indicate the magnitude of influx thatcan be sustained at a given cytoplasmic concentra-tion, i.e. the intensity of negative feedback of inter-nal N accumulation on uptake. The values for NO3

-

are substantially larger than have been observed inother species, including highly efficient NO3

- users;the values for NH4

+ are more typical. This indicatesan unusually high capacity for NO3

- capture and re-tention. There were pronounced differences in sub-cellular N flux partitioning between seedlings pro-vided with NH4

+ and those provided with NO3- (Fig.

5).While similar proportions of incoming N were

channeled into assimilation and to the vacuole, the

4. Concentration-dependence of steady-state NO3– influx (open

symbols) and NH4+ influx (closed symbols) in roots of intact 4-

wk-old IR72 rice. All plants were grown at 100 µM [NO3–]

0 or

[NH4+]

0. Error bars indicate SE (n ≥ 16). IRRI, 1998.

5. Component fluxes of NO3– and NH

4+ as estimated by

compartmental analysis. IR72 rice seedlings were grown andmaintained for 4 wk at 100 µm [NO

3–]

0 or [NH

4+]

0. Total bar

graph heights indicate influx. Component fluxes are efflux fromthe cytoplasm (φ

co), combined flux to assimilation and the

vacuole (φassimilation/vacuole

), and flux to the shoot (φxylem

). Absoluteflux contributions are indicated to the left of respective barsegments, percentages of influx are indicated to the right. Dataare the means of eight to nine experiments (n≥8). SE was lessthan 15%. IRRI, 1998.

8

7

6

5

4

3

2

1

0

0.59

2.27

NO3- NH4

+

3.21 52.92%

9.65%

37.43%

2.01

0.93

0.95

23.9%

24.4%

51.7%

assimilation/vacuole

xylem

co

N flux components (µmol g-1 h-1)

9

8

7

6

5

4

3

2

1

00 100 200 300 400 500

NH4+

NO3

N influx (µmol g-1 h-1)

External N concentration (µM)

–


proportions translocated to the shoot and lostthrough efflux were quite different. Translocation tothe shoot comprised 37% of incoming 13NO3

- butonly 24% of incoming 13NH4

+. In absolute terms,more than twice as much N was made available tothe shoot with NO3

- provision. Given that more than70% of N entering the rice caryopsis and more than50% of N in growing leaves during the grain-fillingstage is derived from remobilization of N storagecompounds accumulated in the shoot during thevegetative stage, this difference is potentially ofgreat significance. Moreover, N loss from the rootsthrough efflux was minimized when NO3

- was pro-vided. Efflux was less than 10% for NO3

- and about24% for NH4

+.Measurements in field experiments with rice in

flooded soil have confirmed high concentrations ofNO3

- in roots and shoots under some circumstances(collaboration with Zhejiang Agricultural University).Hybrids appear to be particularly good in generatingNO3

- in the soil, or capturing it, or both. Althoughsome NO3

- may be lost through denitrification, it maybe that the benefits to the plant of mixed NH4

+-NO3-

nutrition outweigh this. Thus manipulation of theinterchange between N species (for example by man-aging water flow through the field to maximize NO3

-

formation in the rhizosphere) may increase the effi-ciency of N utilization.

Identifying new genes with durableresistance to tungro virusesO. Azzam and E. Coloquio

Screening the rice germplasm collection for sourcesof resistance for tungro viruses includes four evalu-ation tests:

● Initial mass screening of the germplasmaccessions using the Standard evaluationsystem for rice and measuring the symptomseverity and percent infection. This eliminateslines that are susceptible to the vector and theviruses.

● Forced test-tube inoculation and serologicalindexing for resistance to rice tungrobacilliform virus (RTBV) and rice tungrospherical virus (RTSV) using polyclonalantisera raised against each of the viruses. Thisidentifies those lines that are resistant to thevector and to either of the viruses.

● Screening for the vector Nephotettix virescensresistance using the seedbox test. The mortal-ity of the plants based on 1 to 9 score system isused as an indicator of susceptibility orresistance to the green leafhoppers. Thisidentifies which lines have vector (and possiblyvirus) resistance and which ones have virusresistance.

● Further screening of selected lines forresistance to virus strains that are kept on adifferential host. This identifies lines that haveresistance to more than one strain of the virus(using the IRRI greenhouse collection ofstrains).

By 1996, 1,277 lines from Bangladesh, Pakistan,India, Sri Lanka, and Indonesia were screened us-ing the forced test-tube inoculation and serologicalindexing against the RTSV and RTBV polyclonalantisera. Results were that 336 lines had 0% infec-tion with RTSV and 264 lines had <10% infection.For RTBV, only 3 lines showed 0% infection but109 lines had <30% infection. In 1997 and 1998, the336 selected lines with 0% infection for RTSV andthe 3 RTBV lines were screened against tungro vi-rus strains. Three previously identified RTBV-re-sistant lines were not resistant when tested with themixture of RTBV strains in the greenhouse. Forty-five out of the 109 RTBV-tolerant lines (<30% in-fection) are still being evaluated for RTBV resist-ance by insect and Agrobacterium-mediated inocu-lations.

Evaluation results for the 336 lines againstRTSV-A and RTSV-Vt6, the more virulent and re-sistance-breaking strain on TKM6, are shown inTable 7. Most of the lines have already beenscreened for vector resistance and 17 out of the 52selected lines (0% infection) could be identified aspotential resistance donors for broad RTSV resist-ance. Most of those lines are from Bangladesh andIndia.

Development of rice blast-resistantmonogenic linesH. Kato and M. Yanoria

For developing durable resistance against rice blast,pyramiding of major genes, accumulation of minorgenes, a combination of major and minor genes, andmultilines of major genes are considered the effec-


tive methods. Knowledge of the genetic constitutionof major genes in rice cultivars and the pathogenic-ity of blast isolates is a prerequisite for all of thosestrategies. We are establishing simple differentialsystems for the identification of pathogenicity ofblast isolates of each country.

We selected lines with a single resistance genefrom crosses with Lijiangxintuanheigu (LTH) and

resistance gene donor parents (Table 8). LTH is ajaponica variety with no major genes for blast resist-ance. So far, all IRRI blast isolates were compatibleto LTH. Most of the lines probably possess a genefor photoperiod sensitivity from LTH, and thereforeshowed poor growth in the tropics. Harvested seedswere distributed as a set of standard differentials toscientists working with blast and collaborating with

Table 7. Number of accession lines with their resistance reaction to rice tungro spherical virus (RTSV) strains (RTSV-Aand RTSV-Vt6) using forced test-tube inoculation and serological indexing using enzyme-linked immunosorbent assay at21 d post inoculation. IRRI, 1998.

RTSV-Aa RTSV Vt6 strainb

0% infection 0% 1- 10% 11-20% 21-30% 31- 100% Untested

Bangladesh 52 10(19) 8(15) 7(13) 5 (10) 17 (33) 5 (10)Pakistan 10 0 (0) 0 (0) 0 (0) 2 (20) 8 (20) 0 (0)India 261 41(16) 51(19) 36(14) 24 (9) 70 (27) 39 (15)Sri Lanka 2 0 (0) 1(50) 0 (0) 1 (50) 0 (0) 0 (0)Indonesia 11 1 (9) 1 (9) 0 (0) 4 (36) 9 (82) 1 (9) Total 336 52(15) 61(18) 44(13) 36 (11) 98 (29) 45 (13)

aPart of the data for RTSV-A were taken from Cabunagan and Koganezawa, unpubl. data. bNumbers in parenthesis reflect the percentage oflines out of the total lines tested. To ensure that Vt6 strain was used, TKM6 was included in all the experiments as a positive check. Percentinfection of TKM6 ranged between 40 and 86% for the different batches tested.

Origin

Table 8. Rice blast-resistant monogenic lines.

Designation Resistance gene Donor Combinationa Generationb Remarks

IRBLa-A Pi a Aichi Asahi LTH/Donor//LTH BC1F8IRBLa-C Pi a1 CO 39 LTH/Donor//LTH BC1F8IRBLi-F5 Pi i Fujisaka 5 LTH/Donor//LTH BC1F8IRBLks-F5 Pi k-s Fujisaka 5 LTH/Donor//LTH BC1F8IRBLks-S Pi k-s Shin 2 LTH/Donor//LTH BC1F8IRBLk-ka Pi k-s Kanto 51 LTH/Donor//LTH BC1F6Tsuyuake Pi k-mIRBLkp-K60 Pi k-p K60 LTH/Donor//LTH BC1F6IRBLkh-K3 Pi k-h K3 LTH/Donor//LTH BC1F6IRBLz-Fu Pi z(?) LTH/Donor//LTH BC1F8IRBLz5-CA Pi z5 C101A51 LTH/Donor//3*LTH BC3F6 = Pi 2(t)IRBLzt-T Pi zt Toride 1 LTH/Donor//LTH BC1F8IRBLta-K1 Pi ta K1 LTH/Donor//2*LTH BC2F6 = Pi 4(t)IRBLta-CT2 Pi ta C105TTP2L9 LTH/Donor//3*LTH BC3F6 with Pi aReiho Pi ta-2 with Pi aIRBLb-B Pi b BL1 LTH/Donor//LTH BC1F6IRBLt-K59 Pi t K59 LTH/Donor//2*LTH BC2F6IRBLsh-S Pi sh Shin 2 LTH/Donor//LTH BC1F8IRBLsh-B Pi sh BL1 LTH/Donor//LTH BC1F6IRBL1-CL Pi 1 C101LAC LTH/Donor//3*LTH BC3F6IRBL3-CP4 Pi 3 C104PKT LTH/Donor//2*LTH BC2F6IRBL5-M Pi 5(t) RIL249 (Moro.) LTH/Donor//3*LTH BC3F6IRBL7-M Pi 7(t) RIL29 (Moro.) LTH/Donor//3*LTH BC3F6IRBL9-W Pi 9(t) WHD-IS-75-1-127 LTH/Donor//3*LTH BC3F6IRBL12-M Pi 12(t) RIL10 (Moro.) LTH/Donor//2*LTH BC2F6 V86010-RIRBL19-A Pi 19(t) Aichi Asahi LTH/Donor//LTH BC1F8ARL20 Pi 20 Asominori/IR24RIL with Pi a

aLTH= Lijiangxintuanheigu. bGenerations = second crop, 1998.


the International Network for Genetic Evaluation ofRice (INGER).

Sustaining soil quality in intensive ricesystems

Variability of optimal nitrogen applicationsfor riceD. Dawe and P. Moya

Philippine rice farmers vary their nitrogen (N) ap-plication rates substantially from year to year, evenfor the same climatic season. A sample of 32 irri-gated rice farmers in Laguna Province in WSshowed the average difference between maximumand minimum application rates for individual farm-ers during a period of five WS to be 66 kg N ha-1.Socioeconomic factors such as availability of ferti-lizer or biophysical constraints to growth are rea-sons for this variability. To investigate whether suchvariability makes sense, more than 20 yr of datawere analyzed to determine the variability of theo-retical profit-maximizing N rates under experimen-tal conditions at research stations.

The data used were from a series of N responseexperiments at four Philippine experiment stationsduring 1965-88. The experiment stations wereIRRI, the Maligaya Rice Research and TrainingCenter in Muñoz, Nueva Ecija (now known asPhilRice), the Bicol Rice and Corn Experiment Sta-tion in Camarines Sur, and the Visayas Rice Experi-ment Station on Panay Island. Each experimenttypically used five or six different rates of appliedN, usually 0, 30, 60, 90, and 120 kg N ha-1 in theWS, and 0, 60, 90, 120, 150, and 180 kg N ha-1 inthe DS. The varieties used were all modernsemidwarf varieties that originated from breedingprograms at IRRI. Other data were from the Long-term Continuous Cropping Experiment (LTCCE) atIRRI during the same period in which the N re-sponse experiments were conducted. The LTCCEused four different rates of applied N, typically 0,30, 50 (or 60), and 90 (or 100) kg N ha-1 in the WSand 0, 50, 100, and 150 kg N ha-1 in the DS.

Nitrogen response functions were estimated byordinary least squares regression of yield for threevariables: 1) a constant term, 2) the level of appliedN, and 3) the square of the level of applied N. Thisgenerated a quadratic response function, and theoptimal N rate was the point on the response func-

tion where the slope of the function equaled the ra-tio of the N price to price of rice:

where Y represents yield per hectare, N representsN applied per hectare, PN represents the price per kgof N, and PP represents the price per kg of roughrice. Calculated optimal N rates are occasionallylarge (or negative). In such cases, the optimal N ratewas truncated at either 0 kg N ha-1 or 120 kg N ha-1

in WS and 0 kg N ha-1 or 200 kg N ha-1 in DS.

OPTIMAL N RATES

The average optimal WS N rates varied across thefour sites from 52 kg N ha-1 to 72 kg N ha-1, and thestandard deviation varied from 32 kg N ha-1 to 37kg N ha-1. In about 15% of the cases (average acrossstations), the optimal N rate was less than 15 kg Nha-1 (Table 9). The variability of optimal N rateswas similar in the DS, with the mean varying from108 kg N ha-1 to 133 kg N ha-1 and the standard de-viation ranging from 34 kg N ha-1 to 42 kg N ha-1.

Multiple regression analysis was conducted todetermine factors that explain the year-to-year vari-ability at a given site. The most obvious explanationis changing climatic conditions from year to year.This variation was captured by use of dummy vari-ables for each year. Another likely possibility is thatoptimal N rates are different for different IR varie-ties, so dummy variables were also specified foreach variety used. A third possibility is variations inthe indigenous N supply (INS), assuming that theoptimal N rate should vary inversely with INS. Ahigh INS implies it is not necessary to apply largequantities of N, while a low INS implies large quan-tities of N should be added. INS can be defined asN uptake in a zero N plot, but this measure is alsohighly correlated with grain yield in a zero N plot.Because no data on N uptake were available for theN response experiments, grain yield in the zero Nplot was used as an index of INS.

Regression of the optimal N rate on INS anddummy variables for year and variety at each of thefour sites explains 55-70% of the variation in thedependent variable (as measured by the R2) in theWS, and 38-76% in the DS (Table 10). Themagnitudes of the various coefficients (not shown)indicate that year-to-year variations (presumably

dY PN

dN PP=


Table 9. Frequency distribution (in percent) of optimal N rates in experiments at IRRI and three Philippine researchstations. Based on 1965-88 data.

Optimal N rate (kg N ha-1)

Sitea 0-15 15- 30- 45- 60- 75- 90- 105- >120 135- 150- 165- 180- >195 Obser- Av SD30 45 60 75 90 105 120 150 165 180 195 vations

(no.)

Wet seasonBicol 20 7 10 18 20 17 4 0 4 100 52 33IRRI 14 3 6 16 17 16 10 6 12 125 67 37PhilRice 20 3 13 15 16 18 8 2 5 100 56 35VRES 6 5 3 14 21 20 15 7 8 95 72 32 All 15 5 8 16 18 18 9 4 8 420 62 35

Dry seasonBicol 1 0 0 2 7 14 28 25 9 2 4 1 1 5 81 108 34IRRI 2 0 0 1 3 5 17 17 14 11 9 3 3 15 121 131 42PhilRice 1 0 0 0 4 3 15 15 24 9 9 7 1 12 94 133 38VRES 2 0 0 0 9 15 18 29 13 2 4 2 2 5 55 111 36 All 1 0 0 1 5 8 19 20 15 7 7 4 2 10 351 123 40

aBicol = Bicol Rice and Corn Experiment Station, Camarines Sur. VRES = Visayas Rice Experiment Station, Panay Island.

Table 10. Optimal N rate regressed on year dummy vari-ables, variety dummy variables, and indigenous N supply(INS) estimated from grain yield measured in a 0 N con-trol plot. For regressions including data from all sites, yeardummy variables are site-year interactions. IRRI, 1998.

Sitea Coefficient P value R2 ObservationsINS (no.)

Wet seasonIRRI 7.5 0.17 0.55 125PhilRice -23.6 0.00 0.70 100Bicol -12.7 0.03 0.67 100VRES 3.9 0.48 0.69 95 All -3.7 0.18 0.61 420

Dry seasonIRRI 6.0 0.43 0.38 121PhilRice 11.4 0.15 0.68 94Bicol 12.5 0.06 0.52 81VRES 0.3 0.96 0.76 55 All 7.6 0.03 0.55 351

aBicol = Bicol Rice and Corn Experiment Station, Camarines Sur.VRES = Visayas Rice Experiment Station, Panay Island.

due to climate) have larger effects on the optimal Nrate than either variety or INS. This suggests thatreal-time N management, which is able to accountfor changing year-to-year conditions, is the mostimportant factor for optimal crop management.

The coefficient on INS indicates the effect ofINS on the optimal N rate, after controlling for theinfluence of climate and variety. The effect of INSon the optimal N rate is mixed. At PhilRice and

Bicol in the WS, the effect of INS is statistically sig-nificant at the 5% level and negative, as would beexpected. In all other cases, however, the effect ispositive (typically, the positive coefficients are notsignificantly different from zero). The analysis sug-gests that optimal farmer behavior may not neces-sarily result in a negative correlation between INSand applied N. A possible explanation for this resultis that yield in a zero N plot may be a poor measureof INS. More precise measurements of INS wouldbe preferable, but such measurements would also bemore costly and of less ultimate value to farmers informulating cost-effective N management strate-gies.

SPATIAL VARIABILITY AT THE SAME SITE

By using data from different experiments at IRRI,we estimated the spatial variability of optimal Nrates over a relatively small area. For this analysis,data from both the N response experiment at IRRIand LTCCE were used. Experiments were selectedonly if the same variety was used in the same sea-son of the same year. Optimal N rates were calcu-lated for both experiments, and the difference be-tween the two rates was compared. On average, re-gardless of season, the absolute value of the differ-ence in optimal N rates for the same variety and thesame season, at two different sites at IRRI, wasabout 30 kg N ha-1. Part of this difference may be


due to different planting dates, but this spatial vari-ability has implications for the design of yield gapstudies. Yield gap studies in farmers’ fields typi-cally calculate a response function for an entire areaor village, and then compare the behavior of indi-vidual farmers relative to this area-wide responsefunction. The analysis here suggests, however, thatresponse functions may vary significantly over asmall area, casting doubt on the use of a single func-tion for many different farmers.

Practical implications. There are several prac-tical implications of this analysis. First, because op-timal N rates vary substantially from year to year,and because INS appears to help little in explainingthis variation, optimal N management strategiesmust be done in real time, i.e., while the crop is inthe ground. This will most likely require technologysuch as the chlorophyll meter or the leaf color chart,or strategies based on the number of tillers. Wenote, however, that knowledge of the INS is impor-tant to 1) estimate the total crop N demand as a ba-sis for the amount of N to be applied in varioussplits; and 2) decide the need and amount of N ap-plied basally or during early vegetative growth,when plants are too small to be used as an indicatorof N status.

Second, as noted earlier, yield gap studies willprovide more information if response functions areestimated at the level of individual farms instead oflarge areas.

Internal nutrient efficiencies in irrigatedlowland riceC. Witt, A. Dobermann, G. Simbahan,S. Abdulrachman,1 G. Gines,2 W. Guanghuo,3

R. Nagarajan,4 S. Satawatananont,5 T. Son,6

P. Tan,7 and L. Tiem8

In a situation where crop growth is not limited bywater supply, weed problems, or pest infestation,biomass production is mainly driven by the supplyof N. Thus, the demand of the rice plant for othermacronutrients mainly depends on the N supply.There are, however, considerable uncertaintiesabout crop N, P, and K requirements because theinternal efficiencies vary greatly, depending on nu-trient supply, crop management, and climate.

We present the derivation of an empirical modelfor estimating crop NPK requirements in rice,which will be part of a general nutrient decision

support system for improving nutrient managementin intensive rice systems of Asia.

CURRENT SITUATION IN FARMERS’ FIELDS

Within the Mega Project on Reversing Trends ofDeclining Productivity in Intensive Irrigated RiceSystems (RTDP), we have collected a database onnutrient efficiencies in more than 200 farmers’fields. Straw yield, grain yield, components of yield(unfilled spikelets, 1,000-grain weight, number ofpanicles m-2, spikelets m-2), and nutrient concentra-tions of modern, high-yielding varieties were meas-ured using the same methodology at seven sites inChina, India, Indonesia, Philippines, Thailand, andVietnam between 1994 and 1997 (n>800). The dataset covers a wide range of soil nutrient supply, vari-eties, crop management, and climates.

Grain yields ranged from 1.4 to 9.9 t ha-1 with anaverage of 5.1 t ha-1. The average harvest index was0.47. The method of crop establishment greatly af-fected components of yield but differences in grainyield and internal efficiencies among areas withTPR vs WSR were mainly attributed to season- andsite-specific conditions. The total nutrient removalper ton of grain yield in farmers’ fields ranged from10 to 44 kg N, from 0.9 to 9.9 kg P, and from 6 to42 kg K. Across all sites and seasons, average nu-trient uptake requirements were 17.1 kg N, 2.9 kgP, and 16.1 kg K t-1 grain yield. Internal efficienciesranged from 23 to 100 kg grain kg-1 N (mean 58),from 101 to 1069 kg grain kg-1 P (mean 350), andfrom 24 to 179 kg-1 K (mean 62). These are obvi-ously extremely wide ranges representing situationswhere nutrients are either limiting or available insurplus in the plant.

MODELING THE NUTRITIONAL BALANCE

The nutrient requirements of irrigated lowland ricecan be estimated for specified target yields using amodeling approach based on Quantitative Evalua-tion of the Fertility of Tropical Soils (QUEFTS)developed by Janssen and coworkers inWageningen, The Netherlands. The model requiresthe estimation of two boundary lines describing themaximum accumulation and dilution of N, P, and Kin the plant (Fig. 6). These parameters were derivedby exploiting the RDTP database on grain yield andplant nutrient accumulation in aboveground plant


dry matter (DM) at physiological maturity of rice.In addition to the farmers’ data, the database alsocontains data from Long-term Fertility Experimentsat about 15 sites and on-farm trials including nutri-ent omission plots. Therefore, the data used herecover the whole range of possible internalefficiencies of N, P, and K in modern rice varieties(Fig. 6) across a yield range of 6-11 t ha-1.

In QUEFTS, the relation between grain yield andnutrient uptake is assumed to be linear at lower up-take levels because the nutrient uptake would be atits maximum under conditions of limited nutrientsupply. The actual plant nutrient accumulation un-

der such conditions should theoretically be close tothe line of maximum dilution of the respective nu-trient in the plant (e.g., YND in Fig. 6a), but it is notlikely that all major nutrients can be maximally di-luted. Instead, internal efficiencies of all three nu-trients would be between their maximum and mini-mum values in an ideal situation of balanced N, P,and K nutrition so that neither nutrient is limiting oravailable in surplus. This situation is reflected byYN, YP, and YK (Fig. 7).

At elevated yield levels, however, internal nutri-ent efficiencies decrease in a nonlinear fashionwhen actual yields approach the potential yield. The

6. Relationship between grain yield and accumulation of N, P, and K in total aboveground plant dry matter at maturity of rice, based ondata with a harvest index greater than 0.40 kg kg–1. The lines on the left of each figure represent the boundary of maximum dilution ofN (YND), P (YPD), and K (YKD), and the lines on the right indicate the boundary of maximum accumulation of N (YNA), P (YPA),and K (YKA). Slopes of the boundary lines were calculated by excluding the upper and lower 2.5 percentiles of all internal efficiencydata (IE, kg grain produced per kg nutrient in total aboveground dry matter, n ≈ 2,200). The respective slopes for the maximum andminimum IEs are 96 and 42 kg kg–1 for N, 622 and 206 kg kg–1 for P, and 115 and 36 kg kg-1 for K. IRRI, 1998.

7. The balanced N, P, and K uptake requirements (YN, YP, and YK) for targeted grain yields depending on the yield potential (Ymax

) ascalculated by QUEFTS. YND, YPD, YKD, YNA, YPA, and YKA are defined in Figure 6. IRRI, 1998.

10

8

6

4

2

00 50 100 150 200 0 10 20 30 40 0 50 100 150 200

YNDYN

YNA

YPD YP

YPA

YKD YK

YKA

Plant N (kg ha-1) Plant P (kg ha-1) Plant K (kg ha-1)

Grain yield (t ha-1)

Ymax

10 t ha-1

9 t ha-1

8 t ha-1

7 t ha-1

6 t ha-1

11 t ha-1

YKA

YKD

YKD

YPD

YNA

YNDa b c10

8

6

4

2

00 50 100 150 200 0 10 20 30 40 0 50 100 150 200

Plant N (kg ha-1) Plant P (kg ha-1) Plant K (kg ha-1)



nonlinear part of the relationship between grainyield and nutrient accumulation, as predicted by theQUEFTS model, depends on both the definition ofthe boundary lines describing the envelope of maxi-mum and minimum accumulation and on the maxi-mum potential yield that is genetically determined(Ymax, Fig. 7). Assuming that the internal effi-ciencies of modern high-yielding varieties arerelatively similar, the standard boundary lines ofmaximum and minimum nutrient accumulation areapplicable for all tropical and subtropical sites withirrigated lowland rice in Asia (Fig. 6, 7).

On condition that plant growth is limited only bynutrient supply, QUEFTS predicted a linear in-crease in grain yield if nutrients were taken up inbalanced ratios of 14.7 kg N, 2.6 kg P, and 14.5 kgK 1000 kg-1 of grain (internal efficiencies of 68 kggrain kg-1 N, 385 kg grain kg-1 P, and 69 kg grainkg-1 K) until yield targets reached about 70-80% ofthe climate-adjusted yield potential (Table 11).With yields approaching the maximum yield, inter-nal efficiency of N, P, and K decreased. Regardlessof the selected yield potential, the N:P:K in plantDM as recommended by QUEFTS is about5.7:1:5.6 (Fig. 7), which is similar to the averageplant N:P:K of 5.9:1:5.5 that was derived from plantmeasurements at project sites (Fig. 6).

CASE STUDY: MALIGAYA, CENTRAL LUZON,

PHILIPPINES

The concept of nutritional balance is further ex-plained using data from farmers’ fields in CentralLuzon and the experimental station at PhilRice,Maligaya, Philippines. The maximum potentialyield is greater in the DS (10 t ha-1) than in the WS(6 t ha-1), mainly due to lower solar radiation in thelatter. Thus, YN, YP, and YK differ in DS (straightlines) and WS (broken lines) when yields exceed5 t ha-1 (Fig. 8).

Grain yields were usually greater in the DS thanin the WS and there were even clear indications thatplants were N-limited in the DS because most datapoints were closer to the line of maximum N dilu-tion (YND, Fig. 8a). In contrast, most WS datapoints were below the optimum line of N accumu-lation as predicted by QUEFTS (YN, Fig. 8a) and,independent of fertilizer N application, closer to theline of maximum accumulation. The WS resultswere probably caused by unfavorable weather, es-pecially during the grain-filling period. This waswell reflected by the lower harvest index of the WSthan the DS crops (0.42 vs 0.48). Thus, it is eco-nomically reasonable to apply more fertilizer N tothe DS than the WS crops.

Table 11. Balanced uptake requirements, internal efficiencies (kg grain kg-1 nutrient), and reciprocal internal efficiencies(kg nutrient 1,000 kg-1 grain) of N, P, and K for irrigated lowland rice as calculated by QUEFTS to achieve certain grainyield targets. Grain yield potential was set to 10 t ha-1. IRRI, 1998.

Yield Internal efficiency Reciprocal internal efficiency(t ha-1) Required nutrient uptake (kg ha-1) (kg grain kg NPK-1) (kg NPK 1,000 kg grain-1)

N P K N P K N P K

1 15 2.6 15 68 385 69 14.7 2.6 14.52 29 5.2 29 68 385 69 14.7 2.6 14.53 44 7.8 43 68 385 69 14.7 2.6 14.54 59 10.4 58 68 385 69 14.7 2.6 14.55 73 13.0 72 68 385 69 14.7 2.6 14.56 88 15.6 87 68 385 69 14.7 2.6 14.57 104 18.4 103 67 380 68 14.8 2.6 14.77.5 115 20.4 114 65 368 66 15.3 2.7 15.18 127 22.6 126 63 354 64 15.9 2.8 15.78.5 142 25.1 140 60 339 61 16.7 3.0 16.59.0 159 28.2 157 57 319 57 17.6 3.1 17.49.5 182 32.2 180 52 295 53 19.2 3.4 19.09.8 205 36.3 203 48 270 48 20.9 3.7 20.79.9 217 38.6 215 46 256 46 21.9 3.9 21.7

10.0 243 43.1 240 41 232 42 24.3 4.3 24.1


Plant P accumulation was generally close to theline of maximum dilution in both DS and WS crops,which indicates insufficient P supply to the ricecrops (Fig. 8b).

Practical implications. The derived standardmodel (Fig. 7) appears to be valid for all indica ricevarieties with a harvest index of about 0.50 and canbe used regardless of the method of crop establish-ment. Therefore, estimating crop nutrient require-ments within a site-specific nutrient managementapproach in irrigated rice requires no site- or sea-son-specific information other than the climate-ad-justed potential yield, which can be obtained fromcrop simulation models, long-term experiments, orexpertise (Fig. 7).

It is more profitable for farmers to maximize nu-trient efficiencies by a more balanced nutrition thanto aim for yield targets that are approaching themaximum potential yield. The approach usingQUEFTS allows not only the estimation of nutrientrequirements to achieve a certain yield target; it alsoprovides a useful tool for identifying economicyield targets and yield levels at which nutrient usebecomes too inefficient. The nutrient requirementsof rice as defined by using our large data set and the

QUEFTS model were noticeably much lower thanvalues commonly used in the literature.

Increasing water use efficiency in riceculture

Management of cracked soils for watersaving during land preparationT.P. Tuong and R. Cabangon

Drying of a puddled soil during the fallow periodbetween rice crops usually results in soil shrinkageand cracking. Irrigation for land preparation of thenext rice crop, thus, involves water application tocracked rice soils and results in bypass flow throughthe cracks. We hypothesized that measures thatminimize crack formation or impede the flow ofwater through the cracks may reduce these bypassflows and decrease the water requirement. Field ex-periments in the Philippines assessed straw mulch-ing and dry shallow tillage as possible measures toreduce bypass flows during land preparation.

The study was in IRRI fields during the 1993 and1994 DS; in the Angat River Irrigation System,Bulacan, during the 1993 WS; and in Muñoz,

8. Relationship between grain yield and accumulation of N and P in total aboveground plant DM at maturity of rice in Maligaya,Central Luzon, Philippines, 1995-97. Data shown include farmers' fields (27-48 farms) and various field experiments conducted atPhilRice. IRRI, 1998.

10

8

6

4

2

00 50 100 150 200 0 10 20 30 40

Plant N (kg ha–1) Plant P (kg ha–1)


a b

YND

YNA

YPD YP

YPA

YN


Nueva Ecija, during the 1995 DS. Plots (6 m × 11m) at IRRI were sun-dried during the fallow perioduntil irrigation for land soaking for the next ricecrop. Three soil management treatments were im-posed:

● Straw mulching. Rice straw (5 t ha-1) wasbroadcast over the plot 1 d after drainage(DAD). The straw mulch remained on thesoil surface during the fallow period. Thistreatment was not included in 1994.

● Shallow surface tillage. Plots were rototilledto 5-10 cm depth by two passes of rototillerat 18 DAD in 1993 and 14 DAD in 1994.Shallow tillage resulted in a topsoil consistingof clods with an average diameter of about 20mm.

● Control. No treatment was applied during thefallow period.

In Bulacan, six farmers’ fields were selected. InNueva Ecija, the experiment was in eight farmers’fields. Two tillage treatments (control and shallowsurface tillage) were imposed prior to the landpreparation period.

Crack depth and width were monitored at 1- to3-d intervals during the fallow period in one 1- × 1-m subplot in each plot (IRRI Program Report 1995).We also measured irrigation application rates andmonitored the dynamics of the water table and thedistance traveled by the surface waterfront along thecentral longitudinal transect of the control and theshallow tillage field.

The land preparation period was divided into twostages—land soaking (from first water applicationto harrowing) and harrowing stage (from harrowingto leveling). The water flow components in eachphase, expressed in mm of water over each field,can be quantified with the following equation (IRRIProgram Report 1995):

I + R = Ss + Sc + A + E + L

where I = irrigation water; R = rainfall; Ss = surfacewater storage; Sc = crack storage, i.e., the amountof water that fills the cracks in the field; A = waterabsorbed in the topsoil matrix (0-0.2 m depth); E =evaporation from the field; and L = losses.

I, R, Ss, and E were measured directly, Sc fromvolume of cracks, and A from the changes in soilmoisture contents. Losses were derived from thedifference between (I + R) and (Ss + Sc + A + E).

Both crack width and depth increased more rap-idly in the control plots than in the mulched plots(Fig. 9). In 1993, at the end of the fallow period, thecrack width in the mulch treatment was signifi-cantly lower than that in the control treatment. Thiscorresponded to wide differences in the final mois-ture content of the soil surface layer in the two treat-ments (data not shown). The final mean crack depthin the mulch treatment was also less, but not signifi-cantly, than that in the control treatment.

During land soaking of the control treatment inNueva Ecija, water in the cracks advanced fasterthan on the soil surface. In the control treatment, thewater table rose close to the soil surface (less than30 cm) at a position 10 m ahead of the advancingsurface waterfront. No significant rise of the watertable was observed ahead of the surface waterfrontin the shallow tillage treatment (Fig. 10). The sur-face waterfront advanced faster in the tilled treat-ment than in the control. Small soil aggregates in theshallow tillage treatment blocked the cracks, madethem discontinuous, impeded the water flow in thecracks, and reduced the recharge to thegroundwater. Less bypass flow meant higher flow

9. Mean crack widths (a) and depths (b) in different treatmentsafter field drainage at the IRRI fields, 1993 DS. Bars indicatestandard errors of the mean values for 55-161 measurements.

0 10 20 30 40 50 60

70

60

50

40

30

20

10

0

140

120

100

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60

40

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a

b

Control 1993

Mulched 1993

Control 1993

Mulched 1993

Rainfall

Days after drainage

Crack width (mm)

Crack depth (mm) Rainfall (mm)


rate was available for the surface water flow, and re-sulted in a faster rate of advance of the surface wa-terfront in the tilled plots. Shallow tillage can thushelp reduce time for land soaking.

Straw mulching, compared with the controlplots, did not significantly reduce the amount of ir-rigation water for land soaking at IRRI. The shal-low-tilled plots used significantly less water for landsoaking than the control plots. This resulted frommuch lower bypass flow in the shallow-tilled plots.The amounts of irrigation water for land soakingand water loss in shallow-tilled plots were signifi-cantly less than in the mulched plots, despite simi-lar crack depths in shallow tillage and in themulched plots. This highlights the importance ofsmall soil aggregates in blocking and impeding wa-ter flow through the cracks.

Shallow surface tillage in farmers’ fields reducedthe total water input for land preparation by 31-34%of the amount needed in the control plots. Much ofthe differences in water use between the two treat-ments occurred before the first harrowing was per-formed. After harrowing, the loss rates were not sig-nificantly different among treatments in bothBulacan and Nueva Ecija. Harrowing broke soilsinto aggregates, which sealed the cracks and pro-duced puddling, which reduced soil permeability.Shortening the duration between land soaking andthe first harrowing may be an important measure toreduce water loss during land preparation.

10. Groundwater profiles with distance from surface waterfrontin control and shallow tillage plots during flood irrigation forland soaking at Nueva Ecija, 1993. Bars indicate standarddeviation for 25 (in the control) and 23 (shallow tillage)measurements.

Water savings during land preparation may in-crease the service area of an irrigation system. Inrainfed areas, shallow surface tillage may also leadto earlier crop establishment and, thus, reduce therisk of late-season drought.

Population dynamics of Echinochloacrus-galli in wet-seeded riceM. Mortimer, R. Lubigan, A. Man,9

P. Vongsaroj,10 and D. Chin7

The Echinochloa species constitute a serious threatto rice production in all rice ecosystems. In irrigatedrice, they are one of the most noxious weed groupsworldwide. They mimic rice in a number of biologi-cal and ecological characteristics and require inte-grated management practices for successful control.An assessment of Echinochloa crus-galli in wet-seeded rice (WSR) was conducted to determine theeffect of early flooding on weed seedling recruit-ment, yield loss in relation to infestation density,and long-term population change.

A field experiment was conducted at sites in Ma-laysia, Thailand, Philippines, and Vietnam. At eachsite, a representative ecotype of E. crus-galli wasseeded to give a range of infestation densities in rep-licated WSR plots. Treatments varied the onset offlooding and compared early flooding (4 DAS) withlate flooding (12 DAS). Seedling counts of E. crus-galli and rice were taken during 14 d following sow-ing. The number of surviving E. crus-galli plants atmaturity was recorded together with seed produc-tion of survivors and rice yields. The experimentwas then continued into the following season. Stud-ies of seedbank longevity were conducted concur-rently with the field experiment. Seeds were buriedin open mesh bags at different depths, samples re-covered at monthly intervals for 12 mo, and the vi-ability of surviving seed determined.

Figure 11 illustrates the representative flux inpopulation size (log scale) of E. crus-galli from aninitial infestation of 1,000 seeds m-2 over two crop-ping seasons. This underlying pattern in the popu-lation dynamics of the weed was common to allsites. Early flooding, as opposed to late flooding,resulted in about 50% seedling mortality and pro-hibited the successive recruitment of seedling co-horts. Surviving plants increased the seed popula-tion size by about two orders of magnitude by thetime of weed seed dissemination at rice harvest

Initialwatertabledepth

Shallowtillage

Control

Surface water

0 1 2 3 4-140

-120

-100

-80

-60

-40

-20

0

2

Distance from surface waterfront (m)

Water table depth (cm)


(stage 2). In the Philippines, the population suffereda 97% loss by stage 3 through seed removal withrice during harvesting and seed germination in thefallow period. However, surviving plants compen-sated by increased seed production to return the to-tal seed population to high densities, by the end ofthe second season.

Rice yield losses due to E. crus-galli were se-vere. Figure 12 illustrates typical yield loss curvesat the Malaysian Agricultural Research and Devel-opment Institute in relation to weed density andflooding time. Yield declined at all sites sharplywith increasing weed density. No statistically sig-nificant differences were detected in yield due toalteration of flooding time within sites. Intersitecomparisons suggested that densities of 10 E. crus-galli plants m-2 resulted in rice yield loss of between0.8 and 1 t ha-1.

The persistence of viable E. crus-galli seedpopulations in the soil was quantified in terms ofthe time taken to decline by 50% (half-lives). No-ticeable differences were evident among sites. Bur-ied seed populations in Vietnam had a half-life of190 d and was independent of burial depth (5 or 15cm), whereas longevity increased with depth atother sites and half-lives in excess of 1000 d wererecorded at 15 cm burial.

11. The population dynamics of Echinochloa crus-galli in wet-seeded IR72, during 1997 WS and DS. Note interrupted time line. IRRI,1998.

12. Yield-density relationships for Echinochloa crus-galli inwet-seeded rice. MARDI, 1996-97.

This study exposed noticeable differencesamong E. crus-galli populations in terms of yieldloss and demographic traits, but the significant re-sult was the importance of early flooding in regu-lating population increase. Advancing the time offlooding was beneficial at all four sites in terms ofreducing seedling recruitment (by up to 50%) anddid not adversely affect final rice yield. This prac-tice, however, was insufficient as a sole long-termmeasure of weed control due to strong compensa-tory processes in the weed species.

1,000,000

100,000

10,000

1,000

100

10

10 14 112 DAS 5 19 109 DAS

Seedlings

Seedlings

Stage 1

Stage 3

Stage 4

Panicles

Panicles

Seeds atharvest

Seeds atharvestStage 2

95% Cl

Seedlings

Fallow1997 DS 1997 WS

Early flooding

Late flooding

Numbers m-2 (log scale)

0 25 50 75 100 125

1

2

3

4Yield (t ha-1)

Weed density (plants m-2)

Early floodingLate flooding


Semidry rice production for irrigation watersavingsS.I. Bhuiyan, D. Tabbal, and E.B. Sibayan

The increasing scarcity of water in irrigated riceareas and competition from industrial, domestic,and nonrice agricultural sectors mean that rice cul-tivation in the future must be more water-efficient.Increased water use efficiency was examined bycollaborative research by IRRI and PhilRice onsemidry rice production system in farmers’ fields atSan Jose City, Central Luzon, Philippines during1995-97 WS. Semidry rice describes a crop estab-lished as dry-seeded rice (DSR) during thepremonsoon period, nurtured as rainfed crop formost of the vegetative growth stage, and then irri-gated during the remaining growth periods.

Our research objectives were to● establish the feasibility and management

requirements of semidry production systemwithin irrigated areas;

● determine opportunities for saving irrigationwater and more effective use of rainfall and toquantify them; and

● identify the requirements for, and assess thepotential impact of, widespread adoption ofsemidry rice system.

Four treatment combinations consisting of twowater regimes during the irrigation period and twoweed control methods in four replications were laidout in farmers’ fields. The two water regimes werecontinuous shallow (2-5 cm depth) standing waterand continuously saturated soil, while the two weedcontrol methods were recommended chemical weedcontrol and chemical weed control plus hand weed-ing.

The data from the field experiments were supple-mented by data from a survey of 21 randomly se-lected farmers to assess their perceptions on the fea-sibility and practical applicability of semidry ricecultivation. In 1998 WS, four farmer collaboratorsvolunteered to adopt the semidry rice productiontechnique.

● The 3-yr field experiments showed highpotential for water savings.

● Yields obtained in 1995 WS from plots withweed control by both chemical and handweeding were significantly higher than those

obtained in plots with chemical control (Table12) only. In general, yields in the 1995experiment were relatively lower because oftyphoon damage.

● In 1996 WS, when weed growth was less,hand weeding did not significantly add yieldto that obtained from chemical weed controlonly (Table 12).

● In 1997 WS, the highest yield was 4.7 t ha-1

for the treatment combinations in which theplots have either shallow standing water orsaturated soil condition plus chemical weedcontrol and spot hand weeding. In contrast,average yields in neighboring farms were 4.1 tha-1 for transplanted (TPR) and 3.9 t ha-1 forwet-seeded rice (WSR) (Table 12).

● Irrigation water use for land preparation for alltreatments was basically eliminated. Fieldswere plowed, harrowed, leveled, and seededas dry or moist soil. Rainfall supported seedgermination. Previous water managementstudies in the area had reported average wateruse for land preparation amounting to 740 mmfor the WSR and 895 mm for TPR (IRRIProgram Report for 1993). Those amounts areequivalent to about 40% of total water used inWSR and TPR. The potential amount of waterthat can be saved by a semidry rice system forland preparation is 7,400-8,950 m3 ha-1.

Table 12. Average yield of dry-seeded IR64 in differenttreatment combinations of two water regimes and twoweed control methods at different locations and seasons.Upper Pampanga River Integrated Irrigation System(UPRIIS), Central Luzon, Philippines. 1995, 1996, and1997 WS.

Av yield (kg ha-1)Treatmentcombinationa 1995 WS 1996 WS 1997 WS

(5 sites, (3 sites, (2 sites,2 reps) 4 reps) 4 reps)

TC1 (chemical) 1404.8 c 4292.4 a 4663.7 aTC2 (chemical + hand weeding) 2320.9 b 4383.1 a 4728.0 aTC3 (chemical) 1249.7 c 4142.5 a 4424.0 aTC4 (chemical + hand weeding) 2433.3 b 4201.2 a 4667.2 a Mean 1852.2 4254.8 b 4620.7 b LSD 320.3 944.4 501.0 CV (%) 23.0 8.42 6.35

aTC1 and TC2 = continuous standing water (2-5 cm depth), TC3 andTC4 = continuous saturated soil condition up to field capacity.


● The irrigation water used during the cropgrowth stage was low as rainfall was moreeffectively used and irrigation inputs weresupplemental to rainfall. The average wateruse (irrigation plus rainfall) during the 1995,1996, and 1997 WS ranged from about 1,487mm for the plots with continuous standingwater and 1,231 mm for the continuoussaturated soil conditions (Table 13). Twentyto 30% of those water uses were in termsof irrigation water applied for maintainingcontinuous standing water and continuouslysaturated soil.

● The 21 selected farmers who were interviewedafter the 1997 WS were unanimous in sayingthat the semidry rice production technique isa good alternative to TPR. They emphasizedthat the DSR technique is appropriate,especially when irrigation water is scarce.However, some farmers (15%) expressed theconcern that weed control could become aserious problem, and 5% of farmers perceivedthat the yield may be lower. About 5% offarmers were apprehensive that it would bedifficult to adopt the method in areas withclayey soils because of tillage problems.

● The management of the National IrrigationAdministration in Central Luzon, Philippines,advanced the 1998 cropping schedule by 1 moand conducted a massive campaign for theadoption of semidry rice technology within theservice area of the Upper Pampanga RiverIntegrated Irrigation System (UPRIIS). About2,000 farmers, covering an area of 5,000 ha,adopted the technology.

The average crop cut yields of four farmer coop-erators who volunteered to adopt the technology in1998 WS ranged from 3 to 3.7 t ha-1. A survey of 17randomly selected farmers within the vicinity of theexperimental area, and who also adopted thesemidry rice technology, indicated that about 53%obtained an average yield of 4 t ha-1 which was sta-tistically the same as the yields from their WSR orTPR in the previous 1997 WS (Table 14). About47% of farmers obtained an average yield of 3.4 tha-1, which was significantly lower than in the pre-vious WS. Despite the lower yield, the farmers weresatisfied because they were able to reduce the laborfor transplanting and chemicals and to grow a ricecrop with scarce water supply.

Table 13. Average water usea (mm) of dry-seeded IR64 rice in different treatmentcombinations of two water regimes and two weed control methods at differentlocations and seasons. Upper Pampanga River Integrated Irrigation System, Cen-tral Luzon, Philippines, 1995, 1996, and 1997 WS.

Treatment Seasonb

combination Mean 1995 WS 1997 WS 1997 WS

TC1 (chemical) 1131.2 a 1403.9 a 1976.4 a 1503.8(8.8%) (38%) (50.2%) (32.3)

TC2 (chemical + hand weeding) 1118.4 a 1430.2 a 1863.4 ab 1470.7

(8.0%) (36.6%) (47.9%) (30.8)TC3 (chemical) 1100.8 a 1340.8 a 1279.2 ab 1240.3

(6.8%) (32.7%) (28.5%) (22.7)TC4 (chemical + hand weeding) 1088.3 a 1318.1 a 1257.7 b 1221.4

(5.7%) (31.7%) (27.4%) (21.6)933.1

Mean 1109.7 1389.7 1594.2 1356.8 LSD (.05) 44.3 209.0 501.2 CV (%) 3.47 5.48 16.08

aTotal water use (mm) is irrigation water applied + rainfall. bNumbers in parenthesis are percentof irrigation applied.


Table 14. Average yields (t ha-1) obtained by two groupsof farmer adopters of semidry rice in 1998 WS comparedwith their yields obtained from either WSR or TPR in 1997WS. UPRIIS, Central Luzon, Philippines.

Yield (t ha-1)Farmers' group

DSR WSR or TPR(1998 WS) (1997 WS)

I (high yield, 53%) (n=9) 4.0 a 4.2 a II (low yield, 47%) (n=8) 3.4 a 5.3 b Total (100%) (n=17) 3.7 a 4.7 b

Improving pest management

Motivating farmers to test pest managementchanges through use of printed materials andradioK. Heong

Insecticide use decisions of many rice farmers arebased on perceptions of potential damages andlosses caused by pests. Farmers generally overesti-mate the seriousness of the rice leaffolder from itshighly visible damages and apply insecticides in theearly crop stages. Because perceptions, rather thaneconomic rationale, determine most farmers’ pestmanagement decisions, changing their perceptionsmay help reduce unnecessary spraying. Farmers inLong An Province, Vietnam, were motivated to testa heuristic, “Insecticide spraying for leaffolder con-trol in the first 40 d after sowing is not needed.”

The communication media reached 97% of thefarmers in the study sites with 21,000 households.The leaflet, radio drama, and poster had the most ef-fective reach. During 31 mo after the media cam-paign, farmers’ mean insecticide sprays droppedsignificantly from 3.35 to 1.56 sprays farmer-1 sea-son-1. The proportion of farmers who did not useany insecticides increased from 1 to 32%. Therewere also significant reductions in number of farm-ers spraying at the early crop stages of seedling,tillering, and booting (Fig. 13). Farmers’ percep-tions of leaffolder damage were favorably changed.The proportion of farmers who believed thatleaffolders could cause losses was reduced from 70to 25%. The proportion who believed that early-sea-son spraying was required was reduced from 77 to23%. Farmers’ insecticide spray frequencies and thebelief index were significantly correlated. Cost sav-ing (insecticide and labor) as the most important in-

centive to stop early-season spraying was cited by89% of the farmers. A survey of the other districtsin the province showed that the message reached82% of the province’s 210,000 households. About77% stopped early-season spraying, about 20% hadnot applied any insecticides, and the average insec-ticide sprays was 1.6. That compared with 1.56 instudy sites. The belief index was 8.11, which wasnot significantly different from the study sites. Themedia approach stimulated 15 provincial govern-ments to launch their own program and extendedit to the whole Mekong Delta. That potentiallyreached a farm household population of 2 million.

Testing the validity of surrogate taxa forcanopy and floodwater invertebratesK. Schoenly, H. Justo, Jr., A. Barrion, M. Harris,and D. Bottrell

An issue confronting plant protection specialists ishow to characterize tropical rice ecosystems with itsstaggering biodiversity, interconnectedness, andspatial-temporal flux. One approach, advocated byconservation biologists, is the use of single taxaas surrogates for all taxa. This approach assumesthat the characteristics of single taxa representbiodiversity over wide ranges and disturbance gra-dients.

Surrogate-based methods of biodiversity assess-ment were applied to invertebrate time-series datacollected during DS from a farmer’s irrigated ricefield in Calauan, Laguna Province, Philippines.

13. Rice farmers' insecticide applications in different crop stagesin Tan Tru and Tan Thanh districts, Long An Province, Vietnam,before (Aug 1994) and after (Feb 1996 and Mar 1997)introduction of the communication media materials.

100

80

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40

20

0Seedling Tillering Booting Heading Maturing

Crop stages

August 1994February 1996March 1997

Farmers who sprayed (%)


Canopy and floodwater invertebrates were vacuum-and strainer-sampled, respectively, at roughlyweekly intervals from seedling to harvest (eightsampling dates). The cumulative samples included202 taxa and 9,570 individuals for the plant canopyand 180 taxa and 84,905 individuals for the flood-water.

Because ideal surrogate taxa should be abundant,we analyzed the most common taxa sampled fromthe canopy and floodwater faunas. In each test,time-series abundance of each taxon was plottedagainst time-series abundance of all canopy or allfloodwater taxa, depending on the origin of the sam-ple. To determine the suitability of a surrogate taxonin predicting total invertebrate abundance, we usedthe coefficient of correlation (r), judged at P = 0.05,to test the linear fit of the eight date-specific abun-dance of the independent (surrogate taxa) variableagainst the dependent (all taxa) variable. This pro-cess was repeated for each taxon that fell within the95% abundance threshold, established from rank-abundance curves for canopy (82) and floodwater(24) samples. Because of the small sample size ofeach correlation (n = 8), the likelihood was high thatone observation could bias the regression towardstatistical significance. Therefore, statistical signifi-cance and visual inspection of each correlation wereused as companion tests to make final suggestionsfor surrogate taxa.

Of the 82 taxa that made up 95% of the totalabundance of canopy invertebrates, 5 taxa were sig-nificantly positively correlated with all canopy taxa:veliid bugs (Microvelia douglasi atrolineata),corixid bugs (Micronecta quadristrigata Bredin),mymarid wasps (Anagrus spp.), brownplanthoppers (Nilaparvata lugens Stål) andnotonectid bugs (Anisops sp.). Of these, mymaridsgave the best linear fit to the data. However, for allfive taxa, each correlation was driven by a singleoutlying data point (41 DT) whose subsequent re-moval made each correlation nonsignificant. Owingto their sensitivity to single sampling dates, wejudged these five taxa as unacceptable surrogates ofthe canopy fauna.

Of the 24 floodwater taxa that made up 95% ofthe total abundance of floodwater invertebrates, 5were significantly positively correlated with allfloodwater taxa. After removing single outlyingtaxa, our analysis revealed that all five were accept-able floodwater surrogates: ostracods (Heterocypris

luzonensis), chironomid flies, corixid bugs(Micronecta quadristrigata), hydrophilid beetles,and gastropods (Pila sp.).

Hydrophilid beetles and four other taxa(ostracods, chironomids, corixids, and gastropods)were judged as reasonable surrogates of total flood-water biodiversity (abundance) in the dry season.Conversely, none of the 82 canopy taxa tested werefound to be suitable surrogate taxa of the canopyfauna. The floodwater surrogates satisfied criteria ofease of sampling and continuous presence over thecrop cycle, but whether they also exhibit wide geo-graphical distribution in Asian rice ecosystems re-quires further investigation.

Directional movement of predators betweenthe irrigated rice field and its surroundingsL. Sigsgaard and S. Villareal

Unsprayed irrigated rice fields have proven to be al-most pest-free, largely due to the existing predatorfauna. Early establishment of a predator complexrequires that predators either remain in the field dur-ing fallow or that they move into the field from theoutside.

We assessed the possible impact of nearby sur-roundings supplying predators to a newly estab-lished irrigated rice field or vice versa. Predatorswere trapped in directional pitfall traps. Preliminaryresults of catches around an irrigated rice field atIRRI during the first half of the rainy season of 1998showed that the most common predators caughtwere spiders, ants, and carabids. The most caughtspider was P. pseudoannulata (Fig. 14). The high-est relative abundance of P. pseudoannulata wasfound in the bund, stressing the importance of thishabitat for this important predator of the irrigatedrice agroecosystem. P. pseudoannulata was presentearly and brought its young into the newly estab-lished field. Later the directional movement fromthe field was reversed and the field may havechanged to become a source of P. pseudoannulatato other fields. After harrowing, the number of P.pseudoannulata adults increased, while the numberof 2-10 instar spiderlings was reduced to one-tenth.Mortality inflicted in the less mobile youngerinstars is the most probable explanation. Farm op-erations also affected directional movement. Thus,immediately after rice planting, there was a signifi-cant directional movement of females out of the


field. Results indicate that directional movement be-tween the field and its surroundings, as well as totalcatches of predators, depend on farm operations andcrop age. The bund may be an important source ofpredators for the young rice field.

Seed health evaluation for farmer rice cropmanagementS.D. Merca, L. Diaz, M. Hossain, and T. Mew

A study of seed quality of 590 lots of farmer rice seedfrom Cavite, Laguna and Quezon provinces, Philip-pines, revealed pure seed fraction ranging from 88to 95%, rice mixtures of 4-12%, and a weed seedcontamination of 22-35 weed seeds 40 g-1 of riceseed. Most Nueva Ecija farmer rice seeds were be-low the seed qualities set for certified seeds.

Different seed health practices were evaluated toimprove farmer seed health management. Chemi-cal seed treatment gave an additional yield of 351kg ha-1. Flotation increased yield by 255 kg ha-1 andmanual sorting gave additional yield of 742 kg ha-1.Manual seed sorting consistently gave a significant8-20% increase in grain yield.

Use of high-quality IR64 seeds showed thatphysical quality, seedling vigor, and seed infectionwere significantly different from farmers’ IR64seeds. In the three trials involving 30 farmers sea-son-1 in Nueva Ecija, an increase of 8-14% yield ofhigh-quality IR64 seed over farmers’ IR64 seedswas demonstrated, which indicated a degenerationof potential yield when farmers handle their ownseed production. Farmer seed had varietal mixture,

weed seed contamination, and lower physical quali-ties.

Our findings suggest that the use of high-qualityseeds or certified seeds is imperative to improveyield and realize the genetic potential of improvedrice varieties. An estimated 85-90% of farmers can-not obtain certified seeds. For them, seed healthmanagement is vital to maintain physical and ge-netic purity of improved rice varieties and maintaintheir yield potential.

Coping with global climate change:reducing methane emission from ricefieldsR. Wassmann and R. Lantin

Activities on methane emissions from rice fieldswere conducted at IRRI and at eight collaboratingresearch stations in Asia. Methane emissions weregenerally high in irrigated rice, but could effectivelybe reduced in various environmental settingsthrough mid-season drainage.

The seasonal courses of methane emissions inrainfed rice were determined by precipitation pat-terns. In Jakenan, Central Java, Indonesia, the shiftfrom dry to wet conditions resulted in a gradual in-crease of methane emission rates during the wet-season crop (Fig. 15). The reverse shift from wet todry conditions caused high emissions in the earlystage and low emissions in the late stage of the en-suing dry-season crop.

In deepwater rice, average fluxes were relativelylow while cumulative values were high due to long

14. Relative abundance of the most common predators caught in pitfall traps in the bund (n = 90), and with blower-vac (bv) in the bund(n = 72), the field (n = 480), and in uncropped area next to the field (n = 24).

Field-bv

Uncropped- bv

Bund-bv

Bund-pitfall

0 20 40 60 80 100

Percent of total number caught

Habitat and trap type

P. pseudoannulata C. formosana Other spiders P. javanus Other carabids

S. geminata Pheidole sp. Other ants E. stali


15. Methane emission rates (area) and rainfall (bars) during two consecutive seasons (1996-97) in Jakenan, Central Java, Indonesia.

15 Oct 14 Nov 14 Dec 13 Jan 12 Feb 14 Mar 13 Apr 13 May

1997 DS1996-97 WS

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Methane emission(mg CH4 m-2 d-1) Rainfall (mm)

duration of flooding in a given season. Irrespectiveof the ecosystem, methane emission rates were ex-tremely sensitive to quantity and quality of organicamendments. The mode of fertilizer applicationseemed to have only a minor effect on emissionrates. Direct seeding yielded substantially loweremission rates throughout the season.

The impact of rice varieties on methane emis-sions was detectable in field and greenhouse experi-ments, but was in a smaller range than the impact ofwater regime and organic inputs. Furthermore, themethane emission potential of a given cultivarshowed a pronounced variability, depending on thenutritional status of the plant. Phosphorus defi-ciency increased root exudation and, in the nextstep, enhanced methane production and emission. Inall cultivars, the plant’s methane transport capacitywas linearly correlated to tiller numbers, indicatingthat methane transport is determined by outletsrather than biomass. Results in 1998, however, didnot allow a distinct classification of rice cultivarsaccording to emission potentials.

The experimental findings of the project were in-corporated in a model to simulate methane emis-sions from rice fields. The CERES-Rice crop simu-lation model was used as a basis, with existing rou-tines simulating soil organic matter decompositionto predict the amount of substrate available formethanogenesis. This was linked to a submodel cal-

culating steady-state fluxes and concentrations ofmethane and oxygen in flooded soils. Extra routineswere also incorporated to simulate the influence ofthe pool of alternative electron acceptors in the soil.

The model was able to explain the seasonal vari-ations in methane emissions in an experiment in-volving mid- and end-season drainage and additionsof organic material. Because the model also predictsgrain yields, it may be further applied to identifysituations for modifying crop management forhigher yields and lower methane emissions.

Irrigated Rice Research ConsortiumR. Zeigler, P. Sta. Cruz, and M.A. Quilloy

The Irrigated Rice Research Consortium (IRRC)aims to develop multi-institutional and multidisci-plinary research partnerships to solve critical pro-ductivity and sustainability problems in the irrigatedrice ecosystem by formally linking highly success-ful, but separate, research initiatives. The Consorti-um’s anticipated impacts are

● Creation of a regionwide, multi-institutional,multidisciplinary, and integrated researchmechanism;

● Increased irrigated rice system productivityand efficiency through balanced and optimumcombination of inputs at high productionlevels;


● Creation of environmentally and ecologicallysound rice production technology throughimproved resource use efficiency and inputmanagement.

During 1998, IRRC activities included● general coordination of IRRC with regard to

its membership, agenda, resource allocation,and related matters;

● conduct of the joint experimentation onnutrient-pest interaction;

● training-planning workshops for the jointexperimentation, and second joint meetings ofthe IRRC, INMNet, and IPMNet steeringcommittees;

● support of Consortium participants in IRRI-conducted training courses; and

● establishment of the IRRC web page.

Under an IRRC-led nutrient-pest interaction ac-tivity, work plans, research protocols, and imple-menting guidelines were developed; participatinginstitutions and scientists were identified; and fieldresearcher capability was calibrated. Field experi-ments were established on pest impact assessmentin the RTDP Project monitoring farms and cropresidue management. Their first cropping cycle wasmonitored. Agreement was reached to include anADB-funded Hybrid Rice Network under theIRRC.

The governance and management of IntegratedPest Management Network (IPMNet), IntegratedNutrient Management (INMNet), (RTDP), and Hy-brid Rice Network (HRNet) in the IRRC will con-tinue to

● explore opportunities for research collabora-tion, direction, and broad resource allocation;

● identify and lay out mechanics for integrationof other networks, projects, and other researchinterfaces in the Consortium; and

● strengthen interdisciplinary research on soiland crop management, professional develop-ment, and interaction among rice scientists inthe Consortium.

Progress of unreported project

Improving the productivity and sustainabilityof rice-wheat systemsJ.K. Ladha

● Soil N supply capacity was found to be higherin rice than in wheat.

● Dynamic nutrient tests for P and K relate wellto yield and P and K uptake.

● Nitrogen use efficiency is lower in rice than inwheat in silt loams but equal in loamy sand.Nitrification-denitrification and leaching arethe main loss pathways.

● Surveys conducted to assess the importance ofpests at Pantnagar and Faizabad in Indiaallowed further documentation of the injuryprofiles of rice (which are dominated bybrown spot disease and weed infestation).

● Soilborne and seedborne rice pathogensassociated with typical crop rotations in thesystem have been characterized in a smallsample of farmers’ fields at Pantnagar, India.This has led to the development of methodsthat will be used on a larger scale.

● Continued collection of on-farm data from therice-wheat system in Pantnagar to analyzetrends in productivity and the profitability ofsite-specific nutrient management.

Program outlook

The program will maintain its efforts toward raisingthe yield plateau by developing the NPT and hybridrices backed up by a systems approach that inte-grates understanding of yield determinants. Radia-tion use efficiency, high yield determining growthpatterns, N source nutrition, new genes for tungroviruses, and blast resistance are some of the re-search considerations that are integrated in thebreeding of the NPT.

The program will work on sustaining soil qual-ity in intensive rice systems. Emphasis will be onoptimal N applications, internal nutrient efficien-


cies, and modeling the nutritional balance, all ofwhich are directed toward sustainable nutrient man-agement in intensively cropped irrigated lowlands.Identification and quantification of key biotic andsoil organic determinants of sustainability and eco-logical resilience will be addressed. Studies on theconstraints to nutrient supply and the developmentof practical approaches through site-specific nutri-ent management technologies in partnership withNARS and farmers are under way.

Efforts are under way to improve water use atfarm and irrigation system levels. That includes sav-ing water during land preparation and within thecultivation period, weed population dynamics inDSR, and crop establishment methods undersemidry production conditions. Understanding ofthe processes of water quality degradation fromagrochemicals and development of feasible optionsfor its alleviation will be a continuing effort.

Characterization of pest problems and generationof practical pest management strategies will be sus-tained.

The IRRC will provide the institutional frame-work for integration of three networks: IPMNet,INMNet, and HRNet, which are involved in help-ing the NARS in developing and using these tech-nologies. This integration of research efforts willlink and better benefit from each other’s experi-ences and outlook. The IRRC will eventually in-clude other aspects of irrigated rice research, suchas the Rice-Wheat Consortium, farm mechaniza-tion, and systemwide program on water manage-ment and global climate change.

Two SDC-supported projects, the IPM Project(within IPMNet) and RTDP Project (withinINMNet), and the ADB-supported Hybrid RiceNetwork (HRNet) have been formally linked in aconsortium mode. The nutrient-pest interaction re-search in intensive irrigated rice systems is underway. Initial research work within IPMNet, INMNet,and HRNet interfaces is expected to start by the year2000. IRRC eventually will include other aspects ofirrigated rice research on water management, farmmechanization, and global climate change.

Research programsRainfed lowland rice ecosystem

MANAGING CROP, SOIL, AND WATER RESOURCES FOR ENHANCED PRODUCTIVITY ANDSUSTAINABILITY 34Rainfed rice and risk-coping strategies (SS) 34Improved water conservation and nutrient use efficiency via subsoil compaction and mineral fertilization (APPA) 36Analyzing weed community dynamics in rainfed lowland rice (APPA) 38

GERMPLASM IMPROVEMENT FOR RAINFED LOWLAND RICE 39Germplasm for rainfed lowland ecosystems (PBGB) 40Breeding materials adapted to drought (PBGB) 40Screening for drought resistance at vegetative stage (PBGB) 41Mechanisms of submergence tolerance and recovery (APPA) 41Phosphorus efficiency (SWS) 43

Organic anion release into nutrient solutions 44Organic anion release into soil 44Phosphate solubilization by organic anions 45

Mapping genes for root traits (APPA) 46Water extraction and recovery ability following drought (APPA) 47

PROGRESS OF UNREPORTED PROJECTS 49Characterizing and analyzing rainfed rice environments 49Addressing gender concerns in rice research and technology development 50Rainfed Lowland Rice Research Consortium 50

PROGRAM OUTLOOK 51


Rainfed lowland rice ecosystem

Rainfed lowland rice is grown on about 25% of theworld’s rice area (nearly 40 million ha) and contrib-utes 18% of the global rice supply. Average yields arelow and farmers grow mainly traditional varieties. Theecosystem has high potential for increasing produc-tion to meet the increasing demand for high-qualityrice.

The objectives of research in the rainfed lowlandrice ecosystem include● better understanding of anthropological, socioeco-

nomic, and biotic components to allow identifica-tion of major constraints and opportunities forimprovement;

● better technology for managing soil, water, andcrop to achieve high yields; and

● high-yielding germplasm adapted to overcome theconstraints of poor soils, drought, and submer-gence.These objectives are pursued in collaboration with

national agricultural research systems (NARS) throughthe Rainfed Lowland Rice Research Consortium(RLRRC).

Managing crop, soil, and water resourcesfor enhanced productivity andsustainability

This project develops systems for improved crop,soil, and water management for sustainable in-creases in productivity. It also identifies and ana-lyzes the processes governing productivity andsustainability of crop production systems in therainfed lowlands. Research covers nutrient and wa-ter management, crop establishment and weed man-agement, and risk management.

Rainfed rice and risk-coping strategiesS. Pandey, R. Villano, F. Lagasca, H.N. Singh,11

D. Naik,12 and D. Behura12

A good understanding of farmer risk managementstrategies is needed to assess responses of farmersto new technologies and policies. Collection offarm-level data was initiated in 1994 inMungeshpur and Itgaon villages of Faizabad, UttarPradesh, India. Thirty farmers from each villagewere selected randomly for in-depth monitoring ofcropping pattern, input use, and income levels. Thetwo villages differed mainly in risk of rice produc-tion due to differential access to irrigation. Theanalyses reported here used panel data for 1994-97.The major characteristics of the study villages aresummarized in Table 1.

The rainfall data from a monitoring station for1994-97 are presented in Figure 1. Based on rain-fall distribution, 1994 is classified as a normal yearand 1995 and 1996 as drought years, with droughtmore severe in 1995.

Rainfed lowland rice ecosystem 35

as crop management practices are reflections of thedifferential levels of risk in the two villages.

The major risk adjustment mechanisms used bythe rice growers in response to rainfall variabilitywere a) changes in rice area, b) changes in methodsof rice establishment, and c) changes in rice varie-ties. Rice area was reduced in 1995 and 1996 in bothvillages in response to delayed start of the rainy sea-son. While some farmers planted less-moisture-sen-sitive crops, such as pulses and maize, others left theland fallow. Changes in rice establishment methodfrom direct seeding to transplanting in years withfavorable early-season rainfall, and vice versa, werepracticed. Farmers were also found to increase thearea growing traditional varieties in years with de-layed rains and expand the area planted to modernvarieties when rains were more favorable.

A major risk adjustment mechanism, when therainy-season crops were adversely affected, was torely on the dry-season (DS) crops such as wheat,oilseeds, and vegetables. Nonrice crops andnonfarm activities were the major sources of in-come that helped cushion the effect of shortage inrice production in the study area. These sources ofincome were more important in Itgaon than inMungeshpur (Table 2).

The extent of adoption of modern varieties wasfound to be positively correlated with farm size, es-

Table 1. Characteristics of two villages in Faizabad, Uttar Pradesh, India, where farm-level data were collected, 1994-97.

Mungeshpur ItgaonCharacteristic

Small Medium Large Overall Small Medium Large Overallfarmers farmers farmers farmers farmers farmers

Irrigated area (%) 93 74 75 85 34 35 39 37Av operational 0.5 1.5 2.2 0.7 0.5 1.4 2.9 1.4 holding (ha)Proportion of land type (%)

Upland 38 44 24 34 59 60 48 55Medium land 6 16 43 14 15 21 34 24Lowland 57 40 33 52 26 20 18 21

Av length of 5 8 12 5 3 8 9 6 schooling of household head (yr)Av household size 7 9 7 7 7 8 9 8 (members)

1. Kharif season rainfall for Mungeshpur, Faizabad, UttarPradesh, India, 1994-97.

The adoption of modern varieties in Mungeshpurwas over 90% of the area. The adoption rate inItgaon was less than 70%. Short-duration varietieswere more popular in Itgaon (55-66% of the area)than in Mungeshpur (25-31%).

Transplanting was the dominant method of riceestablishment in Mungeshpur, whereas direct seed-ing dominated in Itgaon. Overall, the variability ofyield and net returns was higher in Itgaon, whereaverage level of fertilizer use was lower. The differ-ences in productivity and variability of rice as well

Jun Jul Aug Sep Oct

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Rainfall (mm)

19941995

19961997

Long term average


pecially in Itgaon, suggesting the possibility thatlower risk-bearing capacity of small farmers may bea factor constraining the adoption of modern varie-ties. The share of rice in the total income of smallfarmers was also lower than that of the larger farm-ers. Thus small farmers appeared to have developedincome strategies less reliant on rice production.

Given the low share (4-11%) of rice in total in-come (due to small farm sizes, the importance ofpost-rainy season crops, and nonfarm income in thestudy area), the economic benefit from a reductionin variability of income from rice was found to berelatively small (1-3% of total mean income). Nev-ertheless, improvements in the productivity of riceshould be important in increasing farmers’ incomes.

Improved water conservation and nutrientuse efficiency via subsoil compaction andmineral fertilizationG. Trebuil, D. Harnpitchitvitaya,13 G. Pantuwan,13

T.P. Tuong, and L.J. Wade

Rainfed lowland rice, with an average yield of 1.5 tha-1, is grown on some 4.5 million ha of coarse-tex-tured, low-fertility soils in northeastern Thailand.Water stress ensues whenever rains are interruptedfor about a week.

Efficient management of rainwater and nutrientsthrough soil management practices is a key to im-proving the productivity and stability of the ricecrop on such highly permeable soils. Two-factor

field experiments in collaboration with the UbonRice Research Center were conducted during 1993and 1994 wet seasons (WS). The objectives were tostudy the combined effects of soil compaction andfertilization, to quantify the magnitude of the inter-action with different rates and types of fertilizer ap-plication, and to assess the relative impact of sub-soil compaction and mineral fertilization on riceproductivity.

The main plots compared subsoil compactionwith shallow dry tillage (C1), subsoil compactionwith deep dry tillage (C2), and shallow dry tillagewithout compaction (C0). Five mineral fertilizationtechniques were used as subplot treatments: no fer-tilizer (F0), 40-13-25 kg NPK ha-1 in two applica-tions of conventional fertilizer (F1), 40-13-25 kgNPK ha-1 using slow-release fertilizer (F2), 80-26-50 kg NPK ha-1 in two applications of conventionalfertilizer (F3), and 80-26-50 kg NPK ha-1 usingslow-release fertilizer (F4). Soil was compactedwith 10 passes of a vibrating road roller on 15 May1993. Rice seedlings (RD6) were transplanted in allplots.

Subsoil compaction significantly increased pen-etration resistance to at least 75 cm depth, with the15-40 cm layer being the most compacted (Fig. 2).This degree of subsoil compaction obtained on avery coarse-textured soil without removing the top-soil was satisfactory.

Subsoil compaction significantly increaseddepth and duration of floodwater in rice fields(Fig. 3 a,b). Compaction increased total weeks with

2. Soil penetration resistance profiles with and without subsoilcompaction (mean±SE values of three repli-cations), Ubon RiceResearch Center, Thailand, 1993 WS.

0

20

40

60

80

100

120

Soil depth (cm)

0 100 200 300 400 500

Soil penetration resistance (kPa)

C0 = (Uncompacted + shallow tillage)C1 = (Compacted + shallow tillageC2 = (Compacted + deep tillage)

Table 2. Average percentage share of different sources ofhousehold income for two study villages in Faizabad, UttarPradesh, India, 1994-97.

Source Mungeshpur Itgaon

Rice 11 4Wheat 14 13Other cropa 29 28Livestock 5 3Farm labor 3 1Nonfarm activitiesb 37 50Othersc 1 1Total income 100 100Total incomed 460 642 ($ household-1)

aIncludes pulses, mustard, maize, and other rabi and zaid crops.bIncludes services, laborer, business, blacksmith, barber, and pen-sioner. cIncludes sale of fruits and timber products. dExchange rate:US$1 = Rs 38.00.


surface water accumulation from 3.7 and 2.4 wk forC0 to 11.0 and 14.3 wk for C1, and 11.7 and 14.9wk for C2 for 1993 and 1994 WS, respectively. Be-cause three irrigations were applied during the 1993WS, drought stress was far more severe during thenon-irrigated 1994 WS. But following the disap-pearance of surface water, no lasting and graduallyreceding perched water table was observed in thecompacted plots in the later part of the 1994 crop-ping season. Subsoil compaction did not permit anyincrease in cropping intensity through cultivation ofa short-duration upland crop in the post-rainy sea-son. The benefits of subsoil compaction are thuslimited to effects on the performance of the ricecrop.

Although highest grain production was har-vested in compacted plots in 1993 WS, grain yieldincrease due to subsoil compaction was significant(P=0.05) in 1994 WS only (Table 3). Grain yieldwas 2.2 t ha-1 in C2 plots, 1.8 t ha-1 in C1 plots, and0.8 t ha-1 in C0 plots. This confirmed the superior-ity of deeper tillage as observed in previous experi-ments at the same site. Effects of mineral fertiliza-

tion were significant in the 1993 WS only. The F4slow-release fertilizer treatment gave a grain yieldof 3.2 t ha-1 compared with 1.4 t ha-1 in the F0 plots.No significant yield differences between fertilizertreatments were measured in the 1994 WS partlybecause of the severity of drought stress.

With the exception of the effect on rice grainweight in 1994 WS, no significant interaction wasobserved between compaction and fertilizationtreatments. The combination of subsoil compactionand controlled-release fertilizer constituted a way toincrease soil productivity and stabilize rice yields,and improve food security and incomes at the farmlevel.

Among the three factors studied—subsoilcompaction, tillage depth, and fertilization tech-niques—the subsoil compaction had the highestimpact on rice productivity. Although thecompaction technique helped mitigate climatic risk,it did not improve soil water status after the rainyseason, thus excluding the possibility of its use toincrease cropping intensity at Ubon.

Further investigations are needed. Persistence ofthe subsoil compacted layer should be assessed todetermine how long the effect of subsoilcompaction will last.

Table 3. Effects of subsoil compaction and fertilization ongrain yields (t ha-1) of rainfed lowland rice at Ubon RiceResearch Center, Thailand, 1993 and 1994 WS.

Grain yield (t ha-1)Subsoilcompaction Fertilizer treatmentsb

treatmenta

F0 F1 F2 F3 F4 Mean

1993 WS: CV = 19.8%C0 0.9 1.7 1.8 1.5 2.4 1.7 aC1 1.4 2.0 2.3 2.6 3.6 2.4 aC2 1.8 1.9 2.7 2.7 3.5 2.5 aAv 1.4 a 1.9 b 2.3 b 2.3 b 3.2 c

1994 WS: CV = 32.9%C0 0.8 0.4 1.2 0.9 0.6 0.8 aC1 1.9 2.0 1.6 1.6 1.8 1.8 bC2 2.0 2.3 1.7 2.2 2.8 2.2 cMean 1.5 a 1.6 a 1.5 a 1.6 a 1.7 a

aC0 = shallow dry tillage with no subsoil compaction, C1 = shallowdry tillage with subsoil compaction, C2 = deep dry tillage with sub-soil compaction. bF0 = no fertilizer; F1 = 40-13-25 kg NPK ha-1 intwo applications; F2 = 40-13-25 kg NPK ha-1 as slow-release ferti-lizer; F3 = 80-26-50 kg NPK ha-1 in two applications; F4 = 80-26-52kg NPK ha-1 as slow-release fertilizer.3. (a) Floodwater depth (mean±SE values of three replications),

1993 WS; and (b) floodwater depth (positive values) and perchedwater table depth (negative values), 1994 WS, Ubon RiceResearch Center. Harv = harvest; IR2, IR3 = 2nd and 3rdirrigations; PEb, PEe = beginning and end of panicle emergence.

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b

C0 = (Uncompacted + shallow tillage)C1 = (Compacted + shallow tillageC2 = (Compacted + deep tillage)


Analyzing weed community dynamics inrainfed lowland riceM. Mortimer, C. Piggin, and R. Lubigan

Dry, direct seeding (DSR) in rainfed lowlands is analternative to TPR and suited to areas with uncer-tain seasonal rainfall. DSR is sown at the onset ofthe rains into a seedbed that is often rapidly pre-pared. Crop growth is threatened by rapidly grow-ing weed communities, which frequently have morethan 10 species. Farmers typically repeat patterns ofcultural and chemical weed management practiceseach season. Such repeated use of the same weedmanagement over cropping cycles is known to re-sult in mixtures of weed species that escape thecombined effects of weeding practices. Moreover,this process of interspecific selection often results inparticularly intransigent weeds remaining a threat tocrop yield.

A key part of the process of the design of inte-grated weed management systems involves under-standing the factors that drive the shifts in weed spe-cies. A factorial combination of three land prepara-tion (main plot) and five weed management (sub-plot) treatments was imposed in the 1996 WS on afarmer’s field at Tarlac, Philippines. The field hadbeen regularly cropped with rainfed rice. A surveyin the previous cropping season indicated relativehomogeneity in the weed flora. Land preparationtreatments in main plots contrasted conventionalfarmer practice (rototillage, furrowing, and imme-diate seeding) with the use of a stale-seedbed tech-nique designed to remove weeds with glyphosate(applied at two rates) prior to crop establishment.Preemergence herbicides, butachlor and oxadiazon,were applied immediately after crop seeding.Butachlor is recommended for control of annualgrass and sedges and oxadiazon for control of grassand broad-leaved weeds. No manual weeding fol-lowed the herbicide treatments.

The imposition of the stale seedbed delayedcrop planting by 22 d to allow weed emergence. Inconsequence, crops received different precipitationpatterns. Fertilizer was applied both as a basal (60-60-60 kg NPK ha-1) and topdressing (40 kg N ha-1).Details of the treatments are in Figure 4. Weedcommunities were destructively harvested, aftercanopy closure, from a 50- × 50-cm quadrat in eachplot, and the dry biomass measured for each species.

The average yield of IR72 in weed-free plots was1.7 t ha-1.

Redundancy analysis, the canonical form ofprincipal component analysis, was used to examinethe relationship between weed community compo-sition and experimental treatments. This form of or-dination graphically represented similarity amongplots on the basis of species composition, and con-currently, with similarity among species on the ba-sis of occurrence within plots. Ordination axes wererestricted to linear combinations of experimentaltreatments.

Figure 4 presents the biplot describing the rela-tionships between selected individual species andtreatments. A qualitative assessment of the strengthof correlation may be gained by noting the arrows:those pointing in similar directions indicate highpositive correlation, and those opposite to one an-other, a negative one. The cosine of the angle be-tween the arrows of a species and an experimentaltreatment approximates the correlation coefficientbetween that species and the experimental treat-ment. The relative length of an arrow in the biplotis a reflection of the importance of that species ortreatment in describing interrelationships within theordination. The relative proximity of circles in Fig-ure 4 indicates the degree of similarity in the weedcommunity composition of individual plots. Thedistance of the circles from the origin reflects in-creasing diversity in composition.

Plots that received herbicide and hand weeding(lower left quadrant) exhibited no association withany weed species, and contrasted strongly withunweeded plots (upper right quadrant), which weredominated by Ludwigia perennis, Fimbristylismiliacea, and Echinochloa colona. The absence ofa noticeable association of E. colona with any prac-tice reaffirms the hypothesis that this is a generalweed that will persist under all management condi-tions except manual weeding.

The analysis also indicates that two perniciousweeds, Cynodon dactylon and Cyperus rotundus,were strongly associated with farmer’s practice ofland preparation and the sole use of butachlor andoxadiazon, and negatively correlated with the use ofglyphosate in preplanting land preparation. Bothspecies survive extensively by vegetative meansfrom season to season and rototillage alone pro-motes population increase from fragmented stolons


and tuber chains that escaped earlier butachlor andoxadiazon application. Conversely, rototillage com-bined with glyphosate results in high mortalitythrough within-plant translocation of the herbicide.Glyphosate use in land preparation was partiallycorrelated with the abundance of Ischaemumrugosum and Eclipta prostrata. Both of those spe-cies can exhibit delayed germination in rainfed sys-tems, escape being killed by glyphosate duringseedbed preparation, and emerge into a communitydominated by rice but with fewer other weed spe-cies. They may, therefore, increase with the use ofglyphosate in land preparation and require addi-tional postemergence weed control.

Our analyses gave first insights into possibleshifts that may be expected to occur under differingweed management treatments. While not providingunderlying mechanistic explanations and being sea-sonally dependent, the analyses are valuable in thatthey can be conducted in farmers’ fields by experi-mentally overlaying treatments on the indigenousweed flora.

Germplasm improvement for rainfedlowland rice

Germplasm improvement for the rainfed lowlandsis complicated due to the heterogeneity and com-

4. Biplot redundancy analysis of the relationships among weed species and weed management treatments in rainfed DSR. Theordination shows species locations with solid lines and experimental treatments with dotted ones. Circles represent the weedcommunities of different treatments. Numbers indicate unnamed weed species of lesser importance. (See text for explanation.)

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Fimbristylis miliacea

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Cynodon dactylon

Conventional farmerseedbed preparation (G3)

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Butachlor + manual

weeding (W2)

Oxadiazon + manual

weeding (W4)

Unweeded WS

-1.0

Land preparation treatmentsG1. Land rototilled and left for 22 d for weed emergence,

then sprayed with glyphosate at 0.96 kg ai ha-1. Riceseed subsequently sown in rows to a depth of 1-2 cmat 70 kg ha-1

G2. As in G1, but with glyphosate sprayed at 1.2 kg ai ha-1.G3. Land was rototilled, furrowed, and seeded on the

same day. Rice was dry-seeded in rows at a rate of110 kg ha-1.

Weed control treatmentsW1. Butachlor (1 DAS) at 1.5 kg ai ha-1

W2. Butachlor (1 DAS) at 1.5 kg ai ha-1 + 1manual weeding (28 DAS)

W3. Oxadiazon (1 DAS) at 0.625 kg ai ha-1

W4. Oxadiazon (1 DAS) at 0.625 kg ai ha-1 + 1 manualweeeding (28 DAE).

W5. Not weeded.


plexity of the environment. A dispersed breedingprogram based on physiological understanding ofplant adaptation and environmental characterizationhas been established at key representative sites. Itoperates through a shuttle breeding partnership incollaboration with NARS. A methodology for fieldevaluation of GxE interactions was developed, andpreliminary analysis identified principal factors in-fluencing G×E interaction.

An important constraint to adoption of improvedgermplasm that tolerates drought and submergenceis the preservation of traits found in traditionalcultivars that are highly valued by farmers and con-sumers. This problem is approached through farmerparticipatory breeding, and selection of advancedlines to draw on indigenous knowledge of farmers.

Germplasm for rainfed lowland ecosystemsS. Sarkarung

Shuttle breeding programs were strengthened at therainfed lowland key sites. Early-generation materi-als, mainly F2, were evaluated in 1997 and 1998 WSin a wide range of submergence-prone environ-ments in Assam, Bihar, Madhya Pradesh (MP),Uttar Pradesh (UP), Orissa, and West Bengal.Among these sites, only India Gandhi AgriculturalUniversity (IGAU) at Raipur, MP, representsdrought-prone conditions. The eastern states havemore than 14 million ha of rainfed lowland riceareas.

Most of the breeding materials for drought-proneenvironments in Southeast Asia were initiallyevaluated at the Ubon, Thailand breeding site. Thatsite represents intermittent drought during the veg-etative stage. The selected materials, particularlythe early generations starting from F3, were system-atically sent to Lao PDR, the Philippines, andMyanmar with emphasis on favorable rainfed low-land in the latter two countries.

Breeding materials adapted to droughtS. Sarkarung and S. Pushpavesa13

Breeding materials (F2 onward) including nonglu-tinous and glutinous lines were dry seeded in 1998WS at the Ubon Rice Research Center (URRC).Table 4 shows the number of breeding lines andcrosses for each generation.

In the F2, F4, and F5 generations, in which segre-gation within the lines still prevails, single indi-vidual plants with good agronomic traits were se-lected. A modified bulk method was employed inthe later generations (F6 to F8).

In addition to the breeding activities at URRC,22 advanced breeding lines and 2 check varieties,KDML 105 and RD23, were evaluated on farms atLamplaimat, Buriram, in collaboration with thePopulation and Community Development Associa-tion. Lamplaimat represents a favorable rainfedlowland area of northeast Thailand in the rice-grow-ing areas that produce the best grain quality. Theexperimental plots were dry-seeded on 24 Jun 1998with 25 cm between rows and a 60 kg ha-1 seedingrate.

Table 5 shows grain yields, days to 50% flower-ing, and plant height of the breeding lines and checkvarieties. Many lines yielded significantly higherthan KDML 105. However, IR68835-99-6-7-B,which combines good grain quality with blast resist-ance produced a yield about 15% higher thanKDML 105. On the other hand, IR69550-2-KKN-2-UBN-4-3, even though not producing the highestgrain yields, has grain quality similar to the popularKDML 105. It also has good resistance to blast.

Table 4. Breeding materials evaluated in drought-proneconditions at Ubon Rice Research Center, Thailand, 1998WS.

Lines evaluateda (no.) Plants selected (no.)b

Gene-ration NG G Total NG G Total

crosses crosses

F2 1268 269 49 4129(22) 1173 (24) 49

F4 455 1051 75 570(35) 1517(125) 53

F5 398 949 74 146(47) 700(477) 52

F6 246 405 72 67(34) 331(129) 39

F7 272 337 38 234(59) 795(177) 26

F8 149 1 10 294(36) 3 8

aNG = nonglutinous type, G = glutinous type. bNumber in parenthe-ses is number of lines harvested in bulk.


Screening for drought resistance atvegetative stageS. Sarkarung and G. Pantuwan13

More than 200 advanced breeding lines (F5 onward)were screened for drought tolerance and recoveryability at URRC during 1997-98. Thirty-day-oldseedlings were subjected to different levels of stressafter irrigation stopped. Drought resistance wasscored at 1-wk intervals for 4 wk and recoveryscored 4 d after rewatering. Table 6 presents thedrought resistance score at different stages of stressdevelopment, and their ability to recover afterrewatering. The check varieties were KDML 105(high recovery), NSG19 (drought-resistant), andIR20 (drought-susceptible). The line IR68796-36-2-B-1-1-B gave the lowest drought score and wasthe fastest to resume growth after stress. IR68796-27-3-B-5-2-B and its sister line had low droughtscore and good recovery ability.

Mechanisms of submergence tolerance andrecoveryO. Ito, E. Ella, and N. Kawano

The restoration of normal oxygen conditions duringrecovery of submerged organisms is damaging toplant and animal tissues. An active oxygen-scav-enging system plays an important role in minimiz-ing induction of oxidative stress that may cause li-pid peroxidation, protein denaturation, and DNAmutation. Such a system may include 1) antioxi-dants known as free radical scavengers such as re-duced glutathione and ascorbate, and 2) active oxy-gen-scavenging enzymes such as superoxidedismutase (SOD) and glutathione reductase (GR).Two cultivars, FR13A (submergence-tolerant) andIR42 (submergence-intolerant), were used to con-firm the role of the active oxygen-scavenging sys-tem in protecting the plant from oxidative stressduring recovery from submergence.

Table 5. Grain yields, days to 50% flowering, plant height, and blast reaction of advanced breeding lines evaluated in afarmer’s field at Lamplaimat, Buriram. Thailand, 1998 WS.

Line Grain yield Rank Days to 50% Height Blast scoreb

(t ha-1)a flowering (cm)

IR68835-99-6-7-B 4.7 1 108 138 4IR71505-43-2-B 4.6 2 114 125 3IR69515-27-KKN-3-UBN-6-1 4.6 3 101 116 1IR69515-26-KKN-3-UBN-5-1 4.5 4 108 128 2IR69513-14-SRN-1-UBN-2-B 4.4 5 104 125 4IR69550-3-KKN-1-UBN-12-1 4.4 6 109 110 2IR69550-2-KKN-2-UBN-4-3 4.3 7 104 116 2IR69515-2-KKN-3-UBN-1-3 4.3 8 103 118 4IR69515-10-KKN-3-UBN-B406-2 4.3 9 108 128 3IR69550-2-KKN-1-UBN-5-2 4.3 10 98 107 2IR70220-26-1-B 4.2 11 112 160 3IR69515-26-KKN-3-UBN-4-3 4.2 12 109 127 3IR69515-26-KKN-3-UBN-10-1 4.0 14 105 131 2IR68835-105-1-1-B 4.0 15 110 217 3IR68801-46-1-B-2-B 4.0 16 106 114 3IR69550-2-KKN-1-UBN-4-4 3.7 17 102 106 4IR68815-51-PMI-3-UBN-1-B 3.6 19 104 122 1IR71506-27-2-B 3.6 20 101 113 2IR68801-6-2-B1-2-B 3.3 21 98 124 3IR68796-27-1-B-1-B 3.2 22 101 108 3IR68796-27-1-B-2-B 3.1 23 101 104 2IR68796-27-1-B-5-B 2.9 24 99 105 3Check varietiesRD23 3.7 18 94 105 9KDML 105 4.0 13 119 140 9

CV (%) 13.3LSD (5%) 120.24

aAv of four replications. bStandard evaluation scale for rice (SES) 1 to 9: 1 = highly resistant, 9 = highly susceptible.


The activities of some active oxygen-scavengingenzymes and the levels of antioxidants (reducedglutathione and reduced ascorbate) in the leaves ofseedlings submerged for 6 d were measured.FR13A had significantly higher SOD and GR ac-tivities in the submerged seedlings than in thenonsubmerged control. IR42 had more or less thesame levels of activity under the two conditions

(Fig. 5, 6). Increases in leaf SOD and GR activitiesin FR13A were observed during the first 3 d of re-covery. However, the levels of reduced glutathioneand reduced ascorbate decreased in submergedseedlings in both cultivars. The level of antioxidantsduring the recovery of submerged seedlings in-creased in FR13A at day 5 of recovery for reducedascorbate and at day 7 for reduced glutathione. In

Table 6. Drought resistance and recovery scores of selected breeding lines evaluated at Ubon, Thailand, 1997 DS.

DroughtBreeding line Drought resistance scorea recovery

scoreb

20 Feb 27 Feb 6 Mar 13 Mar 20 Mar 23 Mar

IR70828-18-1-B-B IR54081-CPA-3-B-1-3/ 1.67 3.00 4.00 5.33 5.33 1.67Sabita//SLK3-1-2-2

IR70849-4-3-B-B CT6241-17-1-5-1/ 1.33 2.67 5.00 5.33 5.33 1.67KDML 86G2 4-//IR46329-SKN

IR70849-29-B-B-B CT6241-17-1-5-1/ 2.67 3.33 4.67 5.67 5.67 3.67KDML 86G2 4-//IR46329-SKN

IR68821-70-1-B-5-8-B CT9899-32-1/ 2.33 3.33 4.67 5.67 5.67 1.67IR55829-B-B//IR450-SKN-516

IR68823-9-5-B-1-2-B CT9981-23-5-M-2/ 2.00 2.67 4.33 5.33 5.33 2.33IR55776-16-2//IR54977-UBN

IR69502-28-SKN-1- IR57514-PMI-5-B-1-2/ 1.67 3.00 4.67 5.67 5.33 2.33 UBN-1-B-1 IR57515-PMI-8-1-SKN//

IR43524-55-1-3-2IR69513-1-SKN-2- IR57514-SKN-299-3-2/ 2.33 3.33 4.67 5.67 5.67 3.00 UBN-1-3-2 IR57515-PMI-8-1-SKN//

IR43524-55-1-3-2IR69514-51-KKN-3- IR57514-SKN-299-3-2/ 2.33 2.67 5.00 5.67 5.67 2.33 UBN-1-4-3 IR57515-PMI-8-1-SRN//

IR54119-4-B-1-1IR69514-51-KKN-3- IR57514-SKN-299-3-2/ 2.00 3.00 5.33 6.00 5.67 3.00 UBN-1-5-1 IR57515-PMI-8-1-SRN//



IR54119-4-B-1-1IR68815-51-PMI-2- CT9993-5-10-1-M/ 1.67 2.33 4.67 5.67 5.67 2.33 UBN-7-1-2 IR41431/68-1-2-3//

IR57514-PMI-5-B-1-2IR68815-69-PMI-6- CT9993-5-10-1-M/ 2.33 3.33 4.33 5.67 5.67 1.67 UBN-B-2-1 IR41431/68-1-2-3//

IR57514-PMI-5-B-1-2IR68796-27-3-B-5-1-B CT9992-22-2-4/ 2.33 3.33 5.67 6.67 5.67 3.67

IR56592-21-1-3-1//KDML 105IR68796-27-B-B-6-1-B CT9992-22-2-4/ 1.00 2.33 3.67 5.67 5.67 1.67

IR56592-21-1-3-1//KDML 105IR68796-36-2-B-1-1-1 CT9992-22-2-4/ 1.00 2.00 4.67 5.00 5.00 1.00

IR56592-21-1-3-1//KDML 105ChecksKDML 105 2.33 3.33 5.67 6.37 7.00 4.33IR20 3.33 4.00 6.00 6.67 7.00 5.00NSG19 3.00 4.00 6.47 7.27 7.50 4.73

aAv of four replications. Standard evaluation scale for rice (SES) 1 = highly resistant/very good recovery, 9 = highly susceptible/very poorrecovery. bRecovery score was taken 4 d after rewatering.

Combination


7. Formation of malonylaldehyde (MDA) as an indicator of lipidperoxidation during recovery from submergence for FR13A andIR42. Vertical line indicates LSD (P = 0.05). IRRI, 1998.

6. Activities of glutathione reductase (GR) in leaves duringrecovery from submergence for FR13A and IR42. Vertical lineindicates LSD (P = 0.05). IRRI, 1998.

5. Activities of superoxide dismutase (SOD) in leaves duringrecovery from submergence for FR13A (submergence-tolerant)and IR42 (submergence-sus-ceptible). Vertical line indicatesLSD (P = 0.05). IRRI, 1998.

IR42, the levels remained more or less constant.These findings indicate that high SOD and GR ac-tivities and high levels of antioxidants during recov-ery may explain why FR13A is better at toleratingsubmergence (and thus protect itself from oxidativestress) and has better survival than IR42.

The extent of lipid peroxidation during the firstweek of recovery of submerged seedlings was lessin FR13A than in IR42 (Fig. 7). IR42 may have suf-fered more from oxidative stress than FR13A andthis is consistent with the earlier observation thatFR13A, because of high SOD and GR activities andhigh levels of antioxidant during recovery, may

FR13A, submerged (6 d)FR13A, not submergedlR42, submerged (6 d)lR42, not submerged

0

10

20

30

40

50

0 1 2 3 4 5 6 7Days of recovery

Leaf SOD activity (units mg protein-1)

0 1 2 3 4 5 6 7

50

40

30

20

10

0

Days of recovery

Leaf GR activity (nmole glutathione mg protein-1 min-1)


1 2 3 4 5 6 70

2

3

4

5

6Lipid peroxidation in leaf (nmole MDA g leaf fresh wt-1)

Days of recovery


have protected itself from oxidative stress betterthan IR42.

Phosphorus efficiencyG. Kirk, E. Santos, M. Santos, and G. Findenegg

The mechanisms by which rice roots extract soil Pwas studied to develop a mechanism-based tech-nique for germplasm screening. Earlier research(Program Report for 1992) found that rice plantsgrowing in an aerobic, highly weathered, P-defi-cient soil, with and without added P, were able tosolubilize P and thereby increase their P uptake. Thesolubilization could not be explained by root-in-duced pH changes nor by the release of organic P-mobilizing phosphatase enzymes. It was speculatedthat it might be explained by release of organic ac-ids from the roots.

Other researchers had reported release of citricacid from rice roots into nutrient solution cultures,and we found that the addition of citrate to experi-mental soil released large amounts of phosphateinto solution. To confirm that hypothesis, weneeded to show that the amounts of citrate releasedwere sufficient to explain the observed solubiliza-tion. Organic acids released from roots in soil arequickly decomposed by microbes. Also, any P solu-bilized diffuses into the soil bulk, as well as towardthe root, and not all the P solubilized is taken up.


ORGANIC ANION RELEASE INTO NUTRIENT

SOLUTIONS

Rates of release of organic anions from rice rootsgrown in nutrient solution cultures with and with-out P were measured by transferring the roots of 1-to 3-wk-old intact plants to fresh nutrient solutionsfor 30 min and assaying the organic acids releasedusing high-performance liquid chromatography. Inall the rice cultivars tested, the main organic anionidentified in the exudates was citrate (Table 7).Two, as yet unidentified, organic anions were alsopresent and their excretion consistently increasedabout sixfold under P deficiency. Rates of citrateexcretion also tended to increase under P defi-ciency, though to a lesser extent. Peak rates were ofthe order of 100 pmol g-1 (root fresh weight) s-1.

Rates of excretion differed among cultivars andthere were significant interactions between cultivarsand P status for the two unidentified anions. Malatewas present in the roots at a greater concentrationthan citrate, but rates of malate excretion were neg-ligible (Table 7). The concentration of malate in theroots under P deficiency tended to decrease butthose of the two unidentified anions increased whilethat of citrate was little affected. This indicates thatthe increased excretion of citrate and unidentifiedanions was associated with increases in their ratesof synthesis under P deficiency.

ORGANIC ANION RELEASE INTO SOIL

Rates of organic anion release into soil are likely tobe different from those into nutrient solution cul-tures. Measuring release into soil is complicated bya) decomposition by soil microbes; b) adsorptiononto soil particles, making it necessary to extract thesoil with a reagent to recover the organic anions;and c) interference in the assay of organic anions byother soil constituents extracted. Also, as a result ofadsorption and decomposition, organic anions willdiffuse only a short distance from root surfaces.

To enable recovery of the organic anions re-leased, we grew plants in 3-mm layers of soil. Theroots were arranged in a 2-mm thick, 13- × 8-cmlayer, sandwiched between two 3-mm thick layersof soil connected to a nutrient solution reservoir viaglass-fiber filter paper wicks. Roots were separatedfrom soil by 24-mm-pore-diameter nylon meshsheeting. Two soil P levels (100 and 1000 mg P g-1)and either wholly NH4

+ or NO3- nutrient solution

were used. Organic anions were recovered from thesoil by shaking in 0.01 N H2SO4.

The main organic anion recovered from therhizosphere soil in the thin-layer experiments wascitrate (Fig. 8). Smaller quantities of oxalate,malate, lactate, and fumarate were also detected,and moderate quantities of two unidentifiedcarboxylates and unidentified amino acids. Onlytrace amounts of the organic anions, detected butnot identified in the nutrient solution, were found.

Table 7. Rates of organic anion excretion and concentrations in roots for different rice cultivars grown in nutrientsolution. Rates and concentrations were measured 17 d after planting. Data are means of two replicates. IRRI, 1998.

Rate of excretion (pmol g-1 root FW s-1) Concentration in root (pmol g-1 root FW)

Cultivar Citrate Malate Citrate Malate

+P -P +P -P +P -P +P -P

Salumpikit 11.9 57.8 0 0 0.60 0.24 1.17 0.94Nohrin Mochi 76 36.4 7.5 0 0 0.34 0.31 1.66 0.70Aus 257 17.8 63.1 0 0 0.34 0.46 1.77 1.83WAB56-50 56.7 29.4 0 0 0.36 0.30 1.23 1.14IR55411-50 52.2 51.7 0 0 0.43 0.33 1.08 0.73IAC47 24.7 6.1 0 0 0.33 0.34 1.96 0.85Toyohata Mochi 55.6 124.4 0 0 0.36 0.35 2.71 0.99Azucena 33.6 66.4 0 0 0.27 0.24 1.42 0.68Oryzica Sabana 6 40.0 27.2 0 0 0.32 0.40 1.41 1.06IR47686-09-2-4 0.0 21.4 0 0 0.15 0.17 0.63 0.32


In the P1000 treatments, the citrate concentrationreached steady state after 1-2 wk in which the rateof excretion from the roots was equal to the rate ofdecomposition in the soil. We calculated the appar-ent flux, FC, of citrate across the roots from themeasured steady-state concentration in the soil andindependently measured soil diffusion characteris-tics and rate constant for citrate decomposition.These gave FC = 33 nmol m-2 s-1. The correspond-ing rates of excretion per unit root weight rangedfrom 94 to 43 pmol g-1 (root fresh weight) s-1 overthe course of plant growth. These compared with 34and 66 pmol g-1 (root fresh weight) s-1 under P-suf-ficient and P-starved conditions for the appropriatecultivar (Azucena) in the nutrient solution experi-ments (Table 7).

We assumed that citrate recovered from the thinlayers was all excreted by roots. But it is possible thatpart of it was generated by microbes subsisting onroot-derived carbon in the soil. In this regard, the natureof the unidentified organic anions in the nutrient

8. Amounts of citrate recovered from soil in experiments in which rice plants were grown in thin layers of soil at low and high rates ofP addition. Data are means ± SE of three replications. Dotted lines indicate means over time. IRRI, 1998.

solution experiments, whose synthesis and excretionwere stimulated under P deficiency, is interesting.They may act as substrates for citrate synthesis orotherwise influence its longevity in the rhizosphere.

PHOSPHATE SOLUBILIZATION BY ORGANIC ANIONS

We used the rates of citrate release and decomposi-tion to calculate how much P might be solubilized.To do that, we defined a P-citrate interaction coeffi-cient, l, such that the quantity of P that must be re-moved from the soil for a given uniform addition ofcitrate to leave the P concentration in solution un-changed, equals λbP/bC where bP is the soil P bufferpower (d[P]/d[PL], where [P] equals the concentra-tion of labile P in the whole soil and [PL] equals theconcentration in the soil solution. We measured bP,bC, and λ by shaking the soil with different concen-trations of citrate at a wide range of soil-solutionratios—and a corresponding range of sinks for P—and measuring P and citrate left in solution.

0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7

P100-NO3

P100-NH4

P1000-NO3

P1000-NH4

122

39

250

215

Weeks after transplanting

Citrate in thin layers (µmol system-1)

500

400

300

200

100

0

500

400

300

200

100

0

d

ca

b


We used the values attained together with therates of citrate excretion and decomposition meas-ured above to calculate the extent to which P solu-bilization by rice could be explained by citrate ex-cretion. Figure 9 compares P concentration profilesso calculated with P profiles measured previously(Program Report for 1992). The calculations showthat the observed solubilization and increase in Puptake could indeed be accounted for by citrate re-lease. Running the calculations with FC = 0 showedthat the quantity of P taken up in the absence ofsolubilization was negligible. Given that the modelparameters were measured independent of the out-put, and that the output is sensitive to the parametervalues, the good agreement between the observedand predicted concentration profiles shows that themodel provides a satisfactory description of the sys-tem.

Further research will seek to explain germplasmdifferences in P efficiency in terms of the abovemechanisms, so as to develop a germplasm screen-ing technique.

Mapping genes for root traitsA. Kamoshita, L. Wade, S. Sarkarung, andH.T. Nguyen14

Choice of relevant environments for phenotypicscreening and appropriate mapping populations isessential for identification of quantitative trait loci(QTLs) responsible for traits conferring drought tol-erance, and development of marker-assisted selec-tion technologies. Little attention has been focusedon the screening system for phenotyping of consti-tutive root traits (those conferring a better root sys-tem before the onset of drought) that is relevant torainfed lowland rice.

Variation and QTL for deep and thick root sys-tems were compared for two rice mappingpopulations grown in pots in the greenhouse inanaerobic soil. Comparison was made about 45 dafter sowing for 220 doubled haploid lines from across between breeding lines from upland japonicaand lowland indica (CT9993/IR62266), and 184recombinant inbred lines from a cross within low-land indica (IR58821/IR52561). Thirteen traits, cat-egorized into three groups (shoot, deep root, or thickroot traits) were analyzed in two plantings of con-trasting temperature and radiation conditions (dryand rainy seasons).

9. Observed (points) and predicted (solid lines) concentrationprofiles of P ([P]) in soil near a planar layer of rice roots afterdifferent periods of root-soil contact. Predictions are made witha model of P solubilization by root-released citrate. Dashed linesare predicted citrate concentration ([C]) profiles; dotted lines arepredicted profiles of P in the soil solution ([P

L]). IRRI, 1998.

Distance, x mm-1

35 d

[C]

[PL*]

[P]

14

12

10

8

6

4

2

00 1 2 3 4 5 6

16

12

8

4

0

14

12

10

8

6

4

2

0

[C]

[P]

[PL*]

7 d

16

12

8

4

0

[C]/mmol kg-1, [PL*]/µM[P]/mmol kg-1

[C]

[PL*]

[P]21 d14

12

10

8

6

4

2

0 0

16

12

8

4


Large transgressive variation was observed fordeep root traits in CT9993/IR62266 and for thickroot traits in IR58821/IR52561 (Fig. 10). Genotype× planting interaction was significant but alwayssmaller than genotypic variation with one excep-tion. For deep and thick root traits in IR58821/IR52561, where genotype × planting interaction andgenotypic variation were comparable in size, onlythree out of 22 QTLs identified were commonacross the two plantings. In CT9993/IR62266, sixout of 26 QTLs identified were common for deep orthick root traits, but three of them were also associ-ated with the shoot dry weight and plant height.

We conclude that constitutive root traits may beimproved by crossing within lowland indicas, or by

introgression with upland japonicas. Even subtlevariation in the phenotyping environment influ-enced the QTLs identified, so QTL × environmentinteraction was significant. There was evidence thatdifference in shoot growth affected expression ofroot traits and QTLs identified.

Water extraction and recovery abilityfollowing droughtA. Kamoshita, L.J. Wade, T. Azhiri-Sigari,2 andA. Yamauchi15

Quantitative data are lacking on the dynamics ofplant water use and root and shoot growth in responseto drought and rewatering in rainfed lowland rice.

10. Distribution of deep root dry weight (a,c) and root thickness at 0-10 cm soil depth (b,d) among 220 doubled haploid lines fromCT9993/IR62266 (a,b) and among 184 recombinant inbred lines from IR58821/IR52561 (c,d) in the dry season experiment. IRRI,1998.

40

30

20

10

00.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6

IR62266 CT99930.18

0.16

0.14

0.12

0.10

0.08

0.06

0.04

0.02

0.0

Count Proportion per bar

50

40

30

20

10

0

0.2

0.1

0.00.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

IR62266 CT9993

Count Proportion per bar

0.3

0.2

0.0

0.1

40

30

20

10

0

60

50

0.250.200.150.100.050.0

IR52561 IR58821

Deep root dry weight (g)

40

30

20

10

0

50

1.1 1.2 1.3 1.4 1.5 1.71.6

0.2

0.0

0.1

IR52561 IR58821

Root thickness at 0-10 cm layer (mm)

a b

c d


Shoot and root growth, transpiration, and waterextraction of eight diverse rice lines were quantifiedin three pot experiments: one under severe waterdeficit after panicle initiation (average transpirationof 15.0 mm d-1; Experiment 1), and two under slowand progressive water deficit during tillering (aver-age transpiration of 2.1 and 7.6 mm d-1 in Experi-ments 2 and 3). Higher transpiration was generallyassociated with higher crop growth rate, both earlyin drought development, when soil became aerobicbut soil water was still readily available, and afterrewatering.

Early in drought development in Experiments 2and 3, there was genotypic variation for relativeamounts of tiller and leaf area production comparedwith the well-watered treatment. Genotypes withhigh vigor before stress imposition and during thistransitional phase, such as NSG19, KDML 105,Mahsuri, and IR58821, produced longer root lengthduring the following severe drought period and hadlarger green leaf biomass at the end of the droughtperiod in Experiment 3. These genotypes sharplyincreased transpiration and rapidly expanded leafarea after rewatering, which caused superiordrought recovery (Table 8). In Experiment 1, plantsize before stress imposition was large, and geno-typic variation in response to drought andrewatering was small, except in KDML 105, whichrecovered more rapidly after rewatering.

Both constitutive root traits (those present beforestress) and adaptive root traits (those developed inresponse to stress) varied among genotypes. In well-watered conditions, CT9993 and IR58821 had highroot-shoot ratios, deep and thick root systems, and

high root weights per tiller. In response to milderdrought in Experiments 2 and 3, the total amount ofassimilate distributed to roots was reduced and rootsbecame thinner, but the proportion of total assimi-late supply assigned to deeper layers increased,thereby maintaining deep root mass and increasingbranching.

NSG19, KDML 105, Mahsuri, and IR58821 par-titioned a larger proportion of assimilate to deeproots, had more deep root branching, and took ashorter time to extract 4 kg of soil water duringdrought in Experiment 3 (e.g., 17 d for NSG19 com-pared with 22 d for IR20). The average root lengthdensity below the 30 soil layer was positively cor-related with the rate of water extraction at similardepths during the latter half of the drought period,respectively explaining 66 and 58% of the variationaround 30 and 40 cm depth (Fig. 11).

In Experiment 3, osmotic adjustment tended tobe higher in the genotypes that had a slower rate oftranspiration and a lower pre-dawn leaf water po-tential at the end of drought period. Among thegenotypes that extracted water rapidly, KDML 105had a higher osmotic adjustment. IR58821 andCT9993 had the lowest levels of osmotic adjust-ment.

We conclude that the amount of water transpiredwas more important than water use efficiency indetermining the capacity of a line to perform wellin the imposed conditions of water deficit andrewatering. Vigor before and during transitionalphase from anaerobic to aerobic soil conditions, anda capacity to elongate and branch roots deeply in theprofile as the drought progressed, were advanta-

Table 8. Green leaf biomass at the end of drought period, incremental total root length during the later drought period,transpiration (kg d-1), incremental leaf area (cm-2), and crop growth rate (g pot-1 d-1) during 9 d of rewatering periodamong eight rice genotypes. IRRI, 1998.

Drought RewateringGenotype

Leaf biomass Root length Transpiration Leaf area Crop growth rate(g) (m) (kg d-1) (cm-2) (g pot-1 d-1)

IR20 4.67 d 38.1 c 0.83 c 1783 d 1.36 bNSG19 6.23 ab 59.9 bc 0.97 b 2153 bcd 1.93 aCT9993 5.08 cd 43.6 c 0.81 c 844 e 1.55 bIR62266 5.90 abc 75.2 abc 0.80 c 2442 abcd 1.41 bMahsuri 6.34 ab 108.6 a 0.94 bc 2935 a 2.03 aKDML 105 6.60 a 86.8 ab 1.20 a 2739 ab 2.15 aIR58821 5.69 bc 98.9 a 0.87 bc 2043 bcd 1.89 aIR52561 5.68 bc 43.4 c 0.86 bc 2514 abc 1.56 b LSD (0.05) 0.89 ** 38.8 ** 0.14 ** 683 ** 0.29 **


geous for quicker water extraction during medium-term drought and for superior recovery ability afterrewatering. Root development, water extraction,and other physiological responses need to be exam-ined under more prolonged and severe drought,where seedling vigor may be less important.

Progress of unreported projects

Characterizing and analyzing rainfed riceenvironmentsT.P. Tuong

Characterization of the heterogeneous rainfed riceenvironment for land evaluation in northeasternThailand

11. Relationship between root length density and daily extraction of soil water around 10 (a), 20 (b), 30 (c), and 40 cm depth (d) amongeight genotypes during later half of drought period. IRRI, 1998.

● GIS-based and statistical methodologiesdeveloped for analyzing spatio-temporalvariability of climatic and soil parametersin the rainfed lowland rice environment innortheastern Thailand. Carried out agrocli-matic analysis of northeastern Thailand basedon long-term monthly rainfall and evapo-transpiration data of 16 meteorologicalstations to determine spatial and temporalvariation of rainfall and water balance andduration of humid periods. Generated rainfallprobability surfaces using long-term weeklydata from an additional 100 stations, to be usedfor producing weekly moisture availabilityindex surfaces for drought analysis for thenortheast region. Gridded interpolated sur-

Average root length density (mm-3)

b 20-cm depth

d 40-cm depth

0.0 0.4 0.8 1.2 1.6

100

80

60

40

20

0

a 10-cm depth

100

80

60

40

20

0

c 30-cm depth

0.0 0.4 0.8 1.2 1.6

Daily extraction (g d-1)

IR20

NSG19

CT9993

IR62266

Mahsuri

KDML 105

IR58821

IR52561


faces of various soil fertility parameters weregenerated using geostatistical techniques andwere combined using a mathematical pro-cedure to produce a joint classification of soilfertility for a pilot site in the Ubon land re-form area. This is to be compared with agridded surface of farmers’ assessments of soilfertility.

● Set up pilot study for testing new land useevaluation procedure for a land reform area,Ubon, northeastern Thailand.

Delineation and mapping of intensified rainfedrice areas in the Mekong River Delta

● Methodologies developed for using syntheticaperture radar (SAR) to delineate and maprice-based cropping systems in the MekongDelta.

● Completed mapping of rice cropping systemsusing multidate ERS-2 SAR data for the 1996-97 crop year for a 100 × 100-km area, andcarried out GIS analysis to determineexpansion of intensified double-croppedrainfed rice in relation to the retreat of salinewater intrusion.

● Multidate ERS-2 SAR and RADARSAT datafor the 1997-98 crop year acquired and pre-processed for a 100 × 200-km strip of twoadjacent areas; began preliminary classi-fication and interpretation of the ERS-2 data.

● Field survey data for the 1997-98 crop seasonsfrom seven provinces compiled to provideground truth for validating the map outputfrom radar image processing.

Analyzing sustainability criteria of rainfed rice-based cropping systems in the Bihar Plateau

● Gridded weekly moisture availability indexsurfaces generated for Bihar and West Bengalfor agroclimatic analysis.

● A computer program for determining the startand end of the humid period, as well as theoccurrence of mid-season drought, wasdeveloped for analyzing the weekly moistureavailability index surfaces.

● Block-level and village-level mapping of riceproduction, land use area, and demographiccharacteristics completed for Purulia District.

● GIS data layers of infrastructure, land cover,and economic development generated forGiridih and Purulia districts.

● Household farm survey carried out for eightvillages in Giridih District of Bihar State, dataencoded and ready for economic analysis.Household listing of another eight villages inPurulia District of West Bengal conducted inpreparation for household survey this winter.

Characterizing principal rainfed subecosystems ineastern India

● Validated the GIS and remote sensing-basedmethodology and delineated and characterizedthe rainfed environments at the meso level inMadhya Pradesh.

● Agroecological atlas of eastern India is beingcompiled, featuring climate, land use, land-forms and hydrology, cropping systems, andselected socioeconomic features.

Addressing gender concerns in rice researchand technology developmentT. Paris

● Began impact evaluation of a rice flour milland drum seeder in the Philippines.

● Assessed farmers’ gender-specific criteria forusing traditional and improved rice varieties inthree rainfed villages in eastern Uttar Pradesh,India, under the Farmer Participatory BreedingProject.

● Developed on-farm selection of new rice linesfor rainfed lowland conditions in FaizabadDistrict by male and female farmers.

● Trained NARS partners on data analysis ofsocioeconomic and gender components ofparticipatory research in plant breeding andvarietal selection.

Rainfed Lowland Rice Research ConsortiumC. Piggin

● Workplan meetings for 1998 were held at eachsite from March to May and attended by 4-5IRRI scientists and 20-25 NARS scientists.

● An International Workshop on NutrientResearch in Rainfed Lowlands, which re-


viewed the current knowledge and needs forresearch on nutrients, was held at Ubon,Thailand, 12-15 Oct, and attended by 40NARS, 8 ARI, and 25 IRRI participants. A304-page proceedings was published by year’send.

● The annual steering committee meeting washeld on 15 Oct, after the Nutrient Workshop, toplan 1999 Consortium research and budgets.

● Sixty-four collaborative long- and short-termexperiments (Bangladesh=18; Cuttack,India=6; Faizabad, India=13; Indonesia=7;Philippines=9; Thailand=11) were conductedbetween IRRI and NARS scientists.

● Thirteen research papers were jointly writtenby IRRI and NARS scientists for publication,including 10 papers that summarized researchfindings from RLRRC to be published in aspecial 1999 issue of Experimental Agriculture.

● Two training courses on problem-based tech-nology generation and biometry were con-ducted in Indonesia (15 NARS participants)and Bangladesh (6 NARS participants).

● Six NARS collaborators attended courses onstrategic nutrient management and weedresearch methodologies conducted at IRRIheadquarters.

● Ten NARS collaborators had on-the-jobtraining for 2-4 wk at IRRI headquarters ondata analysis and report writing.

Program outlook

Since the Rainfed Lowland Program began in 1990,substantial progress has been made in clearly defin-ing the problems, understanding the key constraints,and developing workable solutions. The clearer vi-sion of the hydrologic constraints has provided abasis for progress in subecosystem definition,germplasm improvement, cultural intervention, andbetter characterization of target subecosystems.

New tools have been developed to better charac-terize the areas of rainfed lowland and have helpedprioritize future research directions. Varieties betteradapted to the principal constraints of drought andsubmergence have been released, and more will fol-low as integrated efforts among breeders,biotechnologists, and physiologists come to frui-tion.

Our understanding of the genetics and ecology ofblast will result in more stable blast resistance. Bet-ter varieties provide a basis for more accurate agro-nomic interventions in target subecosystems. Inte-grated efforts on agronomic systems, nutrient cy-cling, and weed ecology are providing the depth ofunderstanding needed for successful longer termmanagement of these intensified but risk-reducedsystems. In concert with these efforts, socioeco-nomic (risk management, technology appreciation,and adoption constraints) and gender concerns willbe monitored in village-level studies, and the find-ings considered interactively with other researchoutcomes.

Partnerships in collaboration with NARS arenow providing clear benefits. Research is conductedwhere key constraints are clearly expressed and incollaboration with scientists vitally concerned withsuccessful outcomes. Collaboration with IRRI sci-entists has improved the scientific rigor of researchin the NARS while IRRI has benefited enormouslyfrom the clear priority-setting and outcome focus ofour NARS partners.

The next cycle of research will feature a smaller,more sharply focused agenda. It must address howto improve the reliability of crop establishment indirect seeding, while at the same time ensuring thatweed competition is effectively managed. Earlysowing may permit capture of the early flush of ni-trate at the start of WS. Nutrient manipulation willbe critical to enhancing seedling vigor and then toensuring continued nutrient availability in the com-plex anaerobic-aerobic transitions of the rainfedlowlands. We already have some evidence that nu-trients may partially lessen the adverse effects ofdrought and may enhance survival under submer-gence.

We will focus on these issues because of theirlikely immediate impact. But longer term studieswill continue to ensure the sustainability of increas-ingly more complex cropping systems. Success willultimately depend on adoption of improved varie-ties and technologies. Socioeconomic and genderstudies will provide the basis for developing tar-geted and acceptable packages.

During the next few years, the Rainfed LowlandEcosystem program will make significant advancesin understanding and providing technology for moreproductive and sustainable rice-based cropping sys-tems in the rainfed lowlands.

Upland rice ecosystem 53

Research programsUpland rice ecosystem

IMPROVED PRODUCTIVITY AND SUSTAINABILITY OF FARMING SYSTEMSIN UPLAND RICE AREAS 54Upland rice root system and nutrient effects on its development (APPA) 54

Tiller-nodal root development 55Dynamics of soil and applied nitrogen in upland rice soil culture (APPA) 57A multiscale approach for on-farm erosion research 58

Selected results at field-plot scale (APPA) 58Catchment scale (APPA) 59Farming household scale (APPA) 60

On-farm crop diagnosis of upland rice yields (APPA) 60Cropping patterns and food security in northern Vietnam (SS) 63A characterization of upland rice biotic constraints in Lao PDR (EPP) 64

UPLAND RICE RESEARCH CONSORTIUM (APPA, EPP, PBGB, SS, SWS) 67Progress in 1998 67

PROGRESS OF UNREPORTED PROJECT 67Genetic improvement of upland rice (PBGB, EPP, APPA) 67

PROGRAM OUTLOOK 68


Upland rice ecosystem

Upland rice is grown annually on about 17 million haworldwide—10.5 million ha in Asia, 3.7 million ha inLatin America, and 2.8 million ha in Africa. Totalupland production is about 20 million t. Rice is amajor staple crop for upland farmers in many parts ofAsia, Africa, and Latin America. The total areasupporting upland rice-based cropping is considerablylarger because of rotation with fallow and other crops.The crop is grown alone or in diverse mixtures inshifting or permanent fields under a wide range ofconditions of climate, slope, and soil type, often as asubsistence crop receiving few purchased inputs,although it is commonly a commercial crop receivinginputs in favorable areas such as Brazil, Indonesia,and southern Philippines.

The major thrusts of the program are developingknowledge and technology to maximize productivityand sustainability of upland rice where it is grown,helping maximize returns for farmers’ efforts, andreducing the area needed to satisfy demands forupland rice. Many studies are also providing ascientific understanding with broad application outsidethe upland ecosystem.

The Program has several major themes. Oneinvolves germplasm improvement to overcome majorabiotic (drought, erosion) and biotic (weeds, blast,nematodes) constraints, moving away from traditionalbreeding and selection and using new technologies totarget, characterize, and incorporate desired genes.Two novel projects are on (1) developing a perennialrice for the uplands to help control erosion andimprove food security and (2) investigating allelopathyin rice to assist with sustainable weed management.The perennial upland rice and allelopathy projects arealso providing valuable information on geneticcharacterization of rice and its wild relatives and thegenetics and physiology of tolerance for such con-straints as drought and nematodes.

The second theme is on abiotic constraints,focusing on a strategic understanding of the dynamicsof nutrients (P and N), organic matter, and soil acidityin upland soils. The third theme covers biotic con-straints, investigating the biology and management ofweeds, nematodes, and blast. Underpinning thesethemes is a study of the socioeconomics of theuplands, which is designed to characterize andunderstand the production systems and their dynam-ics and the impact of new technologies and policies.

The Program is implemented in close collaborationwith national agricultural research systems (NARS)through the Upland Rice Research Consortium(URRC), which includes Brazil, India, Indonesia, LaoPDR, Philippines, Thailand, and Vietnam. Bangladesh,China, and Myanmar are associate members. TheConsortium, in operation since 1991 with supportfrom the Asian Development Bank, the GermanAgency for Technical Cooperation (GTZ), and Japan,provides a framework for NARS-IRRI collaboration. Itfocuses on strategic issues and themes of impor-tance to the upland ecosystem. Each partner focuseson a theme and share outputs with others, in whichall share in the planning, implementing, and reportingof the research agenda.

Improved productivity and sustainability offarming systems in upland rice areas

Upland rice root system and nutrient effectson its developmentM. Kondo, P.P. Pablico, D. V. Aragones,R. Agbisit, J. Abe,38 S. Morita,38 and T. Winn

Increased root-length density in upland rice is im-portant for maintaining plant water status. Charac-teristics of root development and nutrient effects onroot distribution were investigated.


TILLER-NODAL ROOT RELATIONSHIP

The structure of the nodal root system in relation totillers and nodes was examined at flowering of twoupland cultivars—low-tillering and deep-rootedMoroberekan and medium-tillering and medium-deep rooted UPLRi-5. They were grown in a rootbox in aerobic soil (soil water content at 35% v/v).Nodal roots per tiller and average length of nodalroots were highest for the main tiller, followed byprimary tillers, and lowest in secondary tillers.Length of nodal roots from main tillers accountedfor 50% of total nodal root length in Moroberekanand 43% in UPLRi-5. Roots from main tillers had asteeper elongation angle than the roots from othertillers, resulting in deeper roots. Root numbers weremore in lower internodes than in higher internodeson a main tiller (Fig. 1). In both Moroberekan andUPLRi-5, nodal roots were longer at the 1st to 4th

internodes compared with higher internodes (Fig.2). The results indicate that stimulating the growthof nodal roots from early internodes in early tillersis likely to promote deeper rooting.

Root development along growth stages. Rootdevelopment and shoot growth for UPLRi-5 weremonitored at an IRRI upland site during 1995 WS.Vertical root distribution, root length depth index(RLDI), and root mass depth index (RMDI), thedepth which contains 50% of roots, were calculatedas

RLDI(cm)={(RL1 × D1) + (RL2 × D2) +(RL3 × D3) +…}/(RL1+RL2+RL3…)

RMDI(cm)={(RM1 × D1) + (RM2 × D2) +(RM3 × D3) …}/(RM1+RM2+RM3…)

whereRLx = root length in the layer x (cm cm-1)RMx = root mass in the layer x (g cm-1)Dx = depth of layer x (cm)

Increase in total root length was at a faster pace thanincrease in shoot dry weight before maximumtillering (Fig. 3). Intrahill root length increased un-til flowering, then decreased sharply while intrarowroot length reached a maximum at panicle initiation.A similar trend was found in root dry weight (datanot shown). The rooting zone expanded both verti-cally and horizontally from crop establishment tomaximum tillering stage and slightly more horizon-

1. Number of nodal roots in internode unit in main tiller inMoroberekan and UPLRi-5 grown in root box for 112 d. IRRI,1998.

2. Average length of nodal roots in internodes in main tiller ofMoroberekan and UPLRi-5 grown in root box for 112 d. IRRI,1998.

tally from maximum tillering to panicle initiation.Maximum rooting depth was attained before maxi-mum tillering. The RLDI and RMDI at panicle ini-tiation were slightly lower than at maximumtillering (Fig. 4). Increased intrarow root length af-ter maximum tillering was probably related to anincrease in shallow nodal roots emerging from latetillers. Thus, there is a close linkage of tillering andnodal root development in the spatial expansion ofthe rice rooting zone.

Moroberekan

UPLRi-5

25.0

20.0

15.0

10.0

5.0

0.01st-3rd 4th 5th 6th 8th7th 9th 10th

Nodal roots (no.)

Internode unit

Moroberekan

UPLRi-560.0

40.0

20.0

0.0

80.0

1st-3rd 4th 5th 6th 8th7th 9th

Internode unit

Average nodal root length (cm)


Effect of P and N on root growth and distri-bution in an acidic Ultisol. The effect of P and Non root distribution at flowering of upland rice wasinvestigated in acidic Ultisols in Siniloan (pH 4.4)and Cavinti (pH 4.5), Philippines. Basal applica-tions of P and N were on the soil surface as singlesuperphosphate and controlled-release urea. Appli-cation of P increased total root length and total rootand shoot dry weights (Table 1). Roots were deeperwith P as indicated by higher RMDI and RLDI.Root length density tended to increase from thesurface to lower layers, especially below 30 cm(Fig. 5). Similar effects of P on roots were observedin Cavinti. Nitrogen tended to increase total rootlength and root dry weight but with a shallower rootdistribution than P.

The results of an experiment that grewMoroberekan and UPLRi-5 in a root box indicatedthat the deeper root distribution with P is mainly as-sociated with stimulated growth of long nodal rootsfrom main and primary tillers. Phosphorus increasedthe number of nodal roots per tiller and the longnodal roots from lower internodes in early tillers,which would lead to the increase in root density indeep layers (Table 2).

Results overall imply that stimulating the devel-opment of main and primary rice tillers by P in theearly vegetative stage results in greater root distri-bution in deeper soil layers during the reproductivestage. Nutrient management in the surface layer sig-nificantly affects the root length density near the soilsurface and in deeper layers.

3. Change in root length and shoot dry weight in UPLRi-5 grownat an IRRI upland site, 1995 WS.

4. Change in tiller number, root length depth index, and rootmass depth index during the growth of UPLRi-5, IRRI, 1995WS.

Table 1. Effect of P and N on shoot and root growth and root depth of an upland ricegrown in Siniloan, Philippines. IRRI, 1998.

Shoot dry Total root Total root Root length Root massEffect weight length dry weight depth index depth index

(g m-2) (m m-2) (g m-2) (cm) (cm)

Effect of NNo N 310a 5161a 143a 23.3a 18.9aN (90 kg ha-1) 356a 5670a 178a 21.3a 15.9b

Effect of PNo P 281b 4075b 123b 19.9b 16.2bP (50 kg ha-1) 385a 6756a 199a 24.7a 18.5a

8000

6000

4000

2000

00 20 40 60 80 100 120

Days after seeding

Total root length in plant rowTotal root length between plant rowsShoot dry weight

Root length (m m-2) Shoot weight (g m-2)

800

600

400

200

0

0 20 40 60 80 100 120

400

300

200

100

0

500 18

16

14

12

10

Days after seeding

Tillers (no. m-2)Root length depth index,root mass depth index (cm)

Root length depth indexRoot mass depth index

Tiller number


Dynamics of soil and applied nitrogen inupland rice soil cultureM. Kondo, P.P. Pablico, D.V. Aragones, andR. Agbisit

Improved N use efficiency is needed for upland ricebecause N recovery is generally low due to NO3

-

leaching. Nitrate in soil solution and soil NO3--N

and NH4+-N were monitored during an upland rice

crop at Batangas (volcanic ash origin, pH 5.18) and

Cavinti (acidic Ultisol, pH 4.50) in 1995 WS, andat Batangas and Siniloan (acidic Ultisol, pH 4.41)in 1996 WS. Applied N in the soil and N recoveryby IRAT216 were traced using 15N.

The amount of NO3- and NH4

+-N were higher inthe Batangas soil in 1996 than in 1995. In 1996, thesoil to 80 cm depth contained 170 kg KCl-extract-able NO3

- and 80 kg NH4+

just after the onset of therainy season. Thereafter, NO3

- decreased sharplyuntil about 60 DAS, possibly due to leaching asrainfall also peaked during this period. Ammoniumlevels remained more constant than NO3

- in all soillayers until crop maturity. A different soil NO3

- pro-file was found in Siniloan and Cavinti. NO3

- in thetop 40-cm layer decreased slowly from the start ofthe crop season, while NO3

- in the 40-80 cm in-creased despite high rainfall.

A positive correlation between KCl-extractableNO3

- and NO3- in soil solution was observed in

Batangas, indicating that most of the KCl-extract-able NO3

- existed in soil solution. In contrast, NO3-

in soil solution was much lower than KCl-extract-able NO3

- in Cavinti and Siniloan. Thus, most of theNO3

- extracted was NO3- absorbed on soil particles

probably by Fe and Al oxides. These results indicatethat high NO3

- sorption capacity reduces NO3-

leaching and maintains high NO3- in subsoil in

acidic Ultisol. This is supported by the observationthat N uptake by rice was higher in Siniloan than inBatangas after heading, possibly due to deeper rootsrecovering NO3

--N from the subsoil.

5. Effect of N and P on root length density of an upland ricegrown in an acidic Ultisol at Siniloan, Philippines, 1998.

Table 2. Effect of P level on number of nodal roots per tiller and number of long nodalroots (>30 cm) in internode units in main tillers in Moroberekan and UPLRi-5 grown in aroot box. IRRI, 1998.

Nodal roots Long nodal roots (>30 cm)Variety and tiller-1 (no.) in internode units (no.)P level

Main tiller Primary tillers 1-4th 5-7th 8th>

MoroberekanNo P 16 2 8 4 0P (0.5 g box-1) 50 19 21 13 4P (1.0 g box-1) 53 19 26 11 0

UPLRi-5No P 14 2 4 4 1P (0.5 g box-1) 38 7 10 6 0P (1.0 g box-1) 44 10 13 8 0

0 0.5 1 1.5 2 2.5 3

75-90

60-75

45-60

30-45

15-30

0-15

Control

+ 90 kg N ha-1

+ 50 kg P ha-1

+ 90 kg N ha-1

+ 50 kg P ha-1

Root length density (cm cm-3)

Depth (cm)


In Batangas, applied 15N recovery by rice wasgreater for late applications than for early applica-tions, possibly a reflection of higher soil N avail-ability early in the season. Early 15N applicationalso resulted in high unrecovered 15N fraction, mostof which was considered lost through leaching. InSiniloan, there was less difference in 15N recoveryamong timings of N application. Siniloan soil re-tained more 15N than Batangas soil, a likely conse-quence of NO3

- absorption in the subsoil. Fifteen to

26% of applied 15N was found in the top 10-cm soilat crop maturity in both sites, presumably incorpo-rated in the soil organic fraction.

In summary, N mineralization upon the onset ofthe rainy season produces high inorganic N in thesurface soil. NO3

- then decreases from the surfacesoil mainly due to leaching of NO3

- and incorpora-tion into organic fraction. NO3

--absorbing capacityof soil significantly affects the level of soil-avail-able N in the root zone. In soils that do not absorbmuch NO3

-, matching N application with N demandof rice would lead to increased N recovery.

A multiscale approach for on-farm erosionresearchGuy Trébuil and F. Turkelboom41

Highland cropping and farming systems in South-east Asia are diversifying rapidly due to populationgrowth and market integration. Farming is charac-terized by an increasing diversity of small farmers’practices and strategies. Research in northern Thai-land showed that the approach using long-term run-off plots and long-term experiments to develop ero-sion control techniques is not adapted to currentfarming circumstances. Alternative approachesshould be based on an understanding of erosionprocesses in farmers’ circumstances at the scale offields, farms, and catchments.

Three research tools were combined: an on-farmerosion survey, a catchment survey, and a farmerclassification (Fig. 6). The research was conductedin Pakha Sukjai, a highland Akha village (800-1100m) of Chiang Rai Province in northern Thailand.Population density was about 65 inhabitants km-2.The area is characterized by a monsoon climate(1,600-2,200 mm rainfall yr-1), a strong relief (slopeangle of 30-70%), phyllite-derived soils, and an ex-tensive range of cropping systems managed on asemipermanent basis.

SELECTED RESULTS AT FIELD-PLOT SCALE

Least erosive rainy event. Rainfall of at least 11mm, a minimum erosivity value of 53 MJ mm ha-1

h-1, a minimum 30-min intensity (I30) of 15 mm h-1,and a duration of at least 37 min was necessary togenerate visually detectable erosion. New erosionsymptoms were always observed for daily rainfallamounts of 20 mm or more.

Typology of erosion symptoms. The corre-spondence found between the diagnosed five stagesof erosion severity and calculated soil losses was auseful tool for roughly, but rapidly, assessing soillosses at field level (Table 3).

Thresholds for slope angles and lengths. Rillscould be observed in nearly every field. Plow layererosion started in fields with slope angles superiorto 47% and lengths superior to 25 m.

Field history and the fallow effect. Erosionsymptoms differed between fields created afterclearing a fallow and older fields. Complementaryexperiments showed that this was due to a high con-tent of fallow vegetation roots in new fields, whichcaused higher macroaggregate stability. This falloweffect disappeared in the second year of cultivation.

Thresholds for soil cover. With more than 50%of total soil cover and 30% of contact cover, erosionwas found to be negligible. These thresholds wereapplied to delimit the duration of the critical peri-ods for erosion.

Delimitation of critical periods for croppingsystems. An erosion efficiency score (EE) of 100%for a given storm means that the maximum increaseof erosion features (from least severe type to themost severe one) was observed in all the monitoredfields. An EE of zero means that no visual changesin erosion symptoms could be detected followingthat specific rain event. Results were that uplandrice displayed a long period (4 mo) of susceptibilityto erosion, while maize, soybean, and cabbage hada 1.5-mo maximum duration of the critical period.This relates to differing evolutions of total soilcover between upland rice (with slower growth rateand more intensive weeding) and the other shorterduration crops.

Delimitation of the high-erosion-risk domain.The integration of the soil cover thresholds enabledthe identification of the field combinations corre-sponding to high erosion risk (Table 4). This matrixis useful in planning appropriate improvements in


land use with farmers, and to provide localstakeholders and decisionmakers with knowledgeof the erosion risk measured at field level.

CATCHMENT SCALE

Because of a mosaic of small fields or fallows andrural infrastructure interrupting runoff flows, only

10% of the gullies observed were developed fromrills in long fields or from runoff that could flowfrom one field into another. Runoff concentrationtook place mainly as the result of contour concavity(36% of cases) or in 49% of the cases because ofrural infrastructure (paths, declining ditches, fieldborder ditches, irrigation channels, paddy terraces,etc.).

6. A proposed multiscale approach for on-farm erosion research. IRRI, 1998.

Spatial distribution of erosion-susceptible household groups

Identification of erosion-susceptible household groups

Identification ofland-use strategyper household group

Identification of erosion-susceptible locations in watershed

Runoff generation Runoff concentration

Identification of erosion-susceptible fields

‘Constant’ field properties Dynamic field properties

- Slope properties

- Soil properties

- Previous land use

- Soil/crop management (land use)

- Soil cover

- Soil roughness

- Erosivity (rain)

- Soil conservation measures

Inter-rills, rills, (gullies)

- Landscape features- Linear rural infrastructure

Gullies and landslides

Field

scale

Catchment

scale

Socioeconomic

and physical

conditions

Village/householdscale

= effect of erosion from one scale to another scale

= effect of land-use dynamics at different scales


FARMING HOUSEHOLD SCALE

Four main types of farming households were iden-tified having different levels of susceptibility to ero-sion risk. Relatively high, and currently not improv-ing erosion risks characterized the profit maximizerand diversifier categories of farms, which repre-sented more than half of the local farming commu-nity. They were seen as the most appropriate targetgroups for participatory soil and water conservationefforts.

The multiscale erosion survey approach is a fastand cheap way to generate new knowledge abouterosion in diverse farming situations. Because ob-

Table 3. Relationship between calculated soil losses and maximum development of observed erosion features at PakhaSukjai, Thailand, 1994 and 1995 WS.

Stagea Year Cropb Calculated Plow Red Rill Pre-rill Pre-rills orsoil loss layer rills network network occasional

(t ha-1 yr-1) erosion rills

5 1995 UR 350 x x x1994 UR 270 x x x x1994 Mz 229 x x x x1994 UR 187 x x x

4 1994 UR 145 (x) x x x1994 UR 108 (x) x x x

3 1994 Bn 64 x x1995 UR 61 x1994 UR 60 x x x1994 Mz 36 x x x

2 1994 Bn 20 x1995 Bn 18 x1994 UR 17 x1995 Mz 13 x1995 UR 10 x1995 Mz 10 x1994 Bn 10 x1995 UR 7 x1994 Mz 6 x1995 UR 6 x1995 Bn 5 x

1 1995 Mz 4 x1995 UR 2 x1995 Mz 2 x1995 UR 2 x

aStage 1: Very mild erosion (0-5 t ha-1 crop-1). Only 1-2 occasional rills (per 10-m contour) and there is low density of pre-rills (<1 per 2-mcontour). Stage 2: Mild erosion (5-20 t ha-1 crop-1). Presence of a pre-rill network (>1 pre-rill per 2-m contour) or more than 3 active rills (per10-m contour). Stage 3: Moderate erosion (20-100 t ha-1 crop-1). Presence of rill network (>1 rill per 2-m) or presence of red rills. Stage 4:Severe erosion (100-150 t ha-1 crop-1). Several active red rills and erosion of tilled topsoil at some local spots. Stage 5: Very severe erosion(150-350 t ha-1 crop-1). Plow layer erosion at the bottom of the field by widening rills or planar slides. bUR = upland rice, Mz = maize, Bn =bean).

servations are made in farmers’ circumstances andaim at understanding the key processes at work, theoutputs are relevant to local issues.

On-farm crop diagnosis of upland rice yieldsK. Van Keer, G. Trébuil, E. Goze, and C. Vejpas

Swidden cultivation of upland rice in northern Thai-land is still an important component of remote up-land farming systems, but yields in farmers’ fieldsare generally low (1-1.5 t ha-1) and variable. Localcultivars display yield potentials of 3-4 t ha-1 in no-input cropping systems. But such potentials are sel-dom reached due to multiple limiting factors. The


importance of successive growth phases in yielddetermination. Identity and causes of yield differen-tiation were assessed by a principal componentanalysis with instrumental variables (PCAIV, log-transformed data for yield components) on 1993-96pooled data as well as for individual year subdatasets.

The study site was characterized by monsoonalclimate, a strong relief, deep granitic soils with clay-loamy texture and medium chemical fertility, het-erogeneous (2- to 10-yr-old) fallow vegetation, anda wide range of weed species, diseases, insects orother pests. Local farmers still use traditionalswidden cultivation practices and no-input croppingsystems. Only limited weed control practices (hoetillage and NaCl application) were observed.

Frequency distributions of phase realization in-dices pinpointed panicle formation and spikelet dif-ferentiation as key periods of yield differentiation(Fig. 7). During the vegetative period, poor cropbiomass accumulation was of greater importancethan low plant densities. Vegetative biomass accu-mulation per plant influenced panicle and spikeletformation, but not spikelet fertilization or grain fill-ing.

Table 4. Effects of slope characteristics and field history on the risk of erosion when soil cover was under the criticalthreshold. Pakha Sukjai, Thailand, 1994 and 1995 WS.

Total Field Slope angle and lengtha

soil croppingcover history <47% 47-57% >57%

<25m >25m <25m >25m <25m >25m

FallowUnder clearingcriticalthreshold 18 7 7 25 50

Olderfield 43 27 14 50 33 51

FallowAbove clearingcriticalthreshold 0 0 33 50 0

Olderfield 33 25 27 0 20 26

a Percentage of field observations in a given situation for which new erosion features were found and measured compared with the previousfield visit—330 field observations analyzed.

identification and ranking of limiting factors, aswell as the understanding of their effects on uplandrice crop functioning, is a prerequisite to setting re-search priorities for improving current practices.

A 4-yr (1993-96) on-farm agronomic survey wasdone in a highland (600-800 m) Lahu village ofnorthern Thailand to

● date and quantify upland rice yielddifferentiation in actual farmers’ conditions,

● characterize upland rice environmentalconditions and farmers’ practices along thewhole crop cycle, and

● identify, rank, and understand the mainenvironmental and cropping system variablesinfluencing upland rice crop production andcausing major yield limitations.

Data on crop population status for two contrast-ing local upland cultivars, crop environmental con-ditions, and cropping practices were obtainedthrough regular monitoring of 432 squares (1 m2

each) delimited at crop emergence in 63 farmers’fields. Phase realization indices, which synthesizethe impacts of crop constraints during a given phaseof upland rice yield buildup, were calculated anddistribution patterns analyzed to assess the relative


7. Frequency distribution of the successive phase realization indices of each growth phase for early and late UR cultivars grown in MaeHaeng. IRRI, 1993-96 pooled data.

100

80

60

40

20

0

100

80

60

40

20

0

100

80

60

40

20

0

100

80

60

40

20

0

100

80

60

40

20

00.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Percentage of squares

Early-maturing varieties (n = 90)

Late-maturing varieties (n = 206)

IPL

IPl

IPlFL

IFL

IGF


The multivariate analysis of pooled data (Fig. 7)revealed strongest negative relationships for

● plant density vs late weed competition andlate-maturing cultivars (lower sowingdensities),

● panicles plant-1 and spikelets panicle-1 vs riceroot aphid infestation, and

● percentage of filled spikelets and 1,000-grainweight vs 1995 wet season (dry spellsoccurred during the wet season).

Weak negative relationships were found forpanicles plant-1 vs slope angle, erosion, number ofsuccessive crops, and early weed stress. The analy-sis of individual year subdata sets isolated rice rootaphid infestation as the single major limiting factorwith a strong and consistent effect on final uplandrice yield.

In Mae Haeng, yield differentiation was found tooccur mainly during biomass accumulation in thevegetative phase and the early part of the reproduc-tive phase. The survey results support the validityof several common hypotheses on limiting factors(weed competition, drought stress, soil erosion). Nomajor soil nutrient as a limiting factor was diag-nosed in this study. The survey showed that moreattention should be paid to soil-borne upland ricepests when prioritizing issues for the improvementof upland rice-based cropping systems in northernThailand highlands.

Cropping patterns and food security innorthern VietnamS. Pandey, T. Blohm,39 Tran van Dien,40 andL. Velasco

A socioeconomic survey of 100 farmers in Bac YenDistrict, Son La Province, examined the effect ofmarket access on the choice of cropping pattern andfood security in the uplands of northern Vietnam. Thevillages of Ta Xua, Hong Ngai, and Phieng Ban weresurveyed to record the cropping pattern, landhold-ing, income sources, and food consumption. Themajor characteristics of the villages are shown in Ta-ble 5. Ta Xua is least accessible to market. PhiengBan is close to the district headquarters. Both Ta Xuaand Hong Ngai have a small proportion of lowlandarea but in Phieng Ban, lowland area accounted for25% of the total landholding. Ethnic groups in TaXua and Hong Ngai are mostly Hmong. In PhiengBan, Hmong, Thai, and Muong are in equal propor-tions.

Lowlands are used for growing summer rice,mostly rainfed. Several crops are grown in the up-lands with maize and upland rice the major ones.The land use pattern in the uplands is most diversi-fied in Phieng Ban, which had high market access,and least diversified in Ta Xua, which had low mar-ket access. Farmers in Phieng Ban have diversifiedtheir cropping patterns to include fruit trees. The

Table 5. Major characteristics of three villages in Bac Yen District, Son La Province,Vietnam, covered by a socioeconomic survey, 1998.

Ta Xua Hong Ngai Phieng Ban

Population density (no. km-2) 17 44 103Market access Low Medium HighFamily size (no.) 12.6 9.0 6.1Lowland area cultivated (ha household-1) 0.59 0.13 0.31Upland area cultivated (ha household-1) 3.1 1.45 0.9Lowland rice area (ha household-1) 0.59 0.13 0.22Upland rice area (ha household-1) 0.5 0.58 0.17Lowland rice yield (t ha-1) 3.2 2.8 4.7Upland rice yield (t ha-1) 1.9 2.5 1.8Lowland rice output (t household-1) 1.9 0.4 1Upland rice output (t household-1) 0.9 1.4 0.3Rice supply (kg capita-1) 227 201 218


Table 6. Average returns to land and labor in lowland rice, upland rice, and maize produc-tion in three villages in Bac Yen District, Son La Province, Vietnam, 1998.

Ta Xua Hong Ngai Phieng BanCrop

Land Labor Land Labor Land Labor($ ha-1) ($ d-1) ($ ha-1) ($ d-1) ($ ha-1) ($ d-1)

Upland rice 273 0.6 363 1.0 268 0.4Lowland rice 474 1.5 405 1.9 685 1.7Maize 124 0.7 160 1.2 202 1.0

importance of upland rice varies among the villages.Average returns to land and labor in the produc-

tion of upland rice, lowland rice, and maize are pre-sented in Table 6. Due to their high returns to land,lowland fields are almost invariably planted to rice.Although returns to land are higher for upland ricethan for maize, high labor requirement for uplandrice, especially for weeding, lowers the returns tolabor. There was an increasing trend toward substi-tution of maize for upland rice in all villages.

Discussions with farmers about changes in crop-ping patterns during 1987-97 indicated three majortypes of adjustments to increased population pres-sure. Farmers in Ta Xua responded by increasing theterraced area to grow lowland rice and by expand-ing upland rice area. A similar expansion of uplandrice was made by farmers in Hong Ngai, but terrac-ing of uplands there was limited due to steeperslopes. Upland rice area in Phieng Ban was reducedover time as land use was increasingly diversifiedand more terraces were constructed in the lowerslopes. Phieng Ban farmers took advantage of themore productive terraced fields for growing rice andgenerated additional incomes through a more diver-sified land use in the uplands.

The total household income per capita in PhiengBan was almost double that in Ta Xua (Table 7).Rice and livestock are important sources of incomein Phieng Ban where markets for small animals,such as pigs and chickens, are readily available. Theeconomy of Phieng Ban is market-oriented and itsshare of cash income in the total income is highestamong the villages. At the same time, the share ofupland rice in the total income is lowest in PhiengBan, indicating that diversification of land use canbe an important mechanism for income enhance-ment in areas with good market access.

The nature of food self-sufficiency was judgedby asking farmers the number of years during thepast 10 yr when rice production was insufficient tomeet their consumption requirement. In Ta Xua andHong Ngai, 20% of the farmers reported no short-age during all of the 10 yr. The corresponding fig-ure for Phieng Ban was 34%. However, about 36%of the farmers in Phieng Ban reported food short-age in each of the past 10 yr. This indicated a some-what bimodal pattern of food self-sufficiency inPhieng Ban with the farmers who had smaller areaof lowlands being less food self-sufficient. Farmersin Phieng Ban were able to maintain their calorieconsumption by purchasing rice in the marketplace. Farmers in Ta Xua and Hong Ngai boughtless rice but increased consumption of maize, cas-sava, and other tuber crops.

The major finding of the study was that althoughthe production of upland rice is less correlated withfood security in areas with better market access anddiversified land use than in other areas, it is of vitalimportance where these conditions are not satisfied.In remote areas with limited lowland area, farmershave little choice but to rely on upland rice for theirsurvival. An increase in productivity of upland ricewill help discourage such farmers from continuingto expand upland rice area into the fragile environ-ments.

A characterization of upland rice bioticconstraints in Lao PDRS. Savary and K. Fahrney

Rice is an important crop in the uplands of LaoPDR, where 219,000 t are produced in a wide rangeof production situations on an area of 340,000 ha.Our analysis refers to farmers’ fields where the


variation in rice yield was from 200 kg to more than3 t ha-1. This is probably a reasonable reflection ofthe range of production situations encountered inthe uplands in Lao PDR, and perhaps in many up-land rice fields of the region.

Alleviation of upland rice pest constraints is sel-dom considered a priority, for a number of possiblereasons:

● secondariness of these constraints relative toothers, such as erosion or soil fertility;

● difficulty of pest management, e.g., soilinsects; and

● lack of documentation on pest importance.The approach was to monitor ongoing on-farm

experiments, quantify crop growth and injuries, andtry to link the resulting groups of variables to yieldvariation. In essence, the objective was not to quan-tify yield reduction due to upland rice pests (weeds,insects, and pathogens), but to identify circum-stances in which those pests may lead to injuries,which in turn may have a potential yield reductioneffect.

Several statistical techniques were used. The firstfollowed the design used in the on-farm experi-ments, with analyses of variances based on theiroriginal design. Because the data sets are suffi-ciently large, principal components, multiple re-gressions (1995 data), and correspondence analysis(combined data sets of 1995 and 1996) were alsoused. Each of these techniques has advantages anddrawbacks. Their combination, however, allowedan overview of complex relationships in the uplandsystem from a plant protection perspective.

● A large and significant variation in yieldacross farmers’ fields, and a small andinsignificant overall variation associated withthe tested N treatment were found. In addition,small but significant variation in yield wasattributed to the site × treatment interaction—the N treatment had a small but significanteffect in some of the farmers’ fields.

● Eigen vectors generated from principalcomponent analysis on crop growth variableswere used as new, composite variables todescribe yield variation using a stepwise,multiple regression analysis. This allowed afair description (50.2% of yield variationaccounted for by the regression) of yieldvariation using four of the six eigen vectorsavailable. Introduction of individual injuries inthe regression model in a stepwise proceduremarginally improved (53.4 %) the fraction ofyield variation explained. Only two injurieswere retained in the final model—leaf blastand weed infestation.

● Relationships among variables are summa-rized in a graphic output of principal compo-nent analysis using its two first axes (25.3 and16.7% of total variance explained, Fig. 8). Notall variables are shown on the graph. Cropdensity (DTY) in an early stage of the crop(Aug, DTY1) and at a later stage (Sep, DTY2),initial number of tillers (TILL1), and leafnumbers (LEAF1 and LEAF2) are associated,reflecting vigorous crop growth. This clusterof variables is associated with (early) leaf blast(LB1) and opposed to weed infestation(WEED1 and WEED2). It also is stronglyopposed to (early) white grub injury (WG1).Early weed infestation (WEED1) is associatedwith (early) brown spot infection (BS1).Figure 8 primarily highlights the collinearityamong variables, especially injuries.

● Collinearity among variables was one amongseveral other reasons to use correspondenceanalysis and derive a more synthetic view ofthe data (Fig. 9), where four broad domains aredefined. Domain A corresponds to presence ofneck blast, whiteheads, and sheath rot, and tohigh levels of brown spot. Domain Bcorresponds to presence of sheath blight andwhite grubs, medium brown spot, and (late)

Table 7. Household income per capita and its composi-tion in three villages in Bac Yen District, Son La Province,Vietnam, 1998.

Ta Xua Hong Ngai Phieng Ban

Total income ($ capita-1) 59 72 114Share of cash income in total income (%) 32 50 63Income shares (%)

Upland rice 19 32 8Lowland rice 37 9 26Other crops 16 17 14Livestock 14 27 34Home gardens 1 4Forest products 1Off-farm 13 14 14


weed infestation, and absence of deadhearts.Domain C corresponds to absence of white-heads and neck blast and to low brown spotand (late) weed infestation. Domain D cor-responds to low defoliator injury, to medium(early) weed infestation, and to high leaf blastand (late) weed infestation. Domains B, C, andD correspond, in turn, to yield levels. DomainC corresponds to very low yields (YLL),domain B to low-medium yields (YL-YM),and domain D to high yields (YH).

This additional analysis was much more power-ful than the previous parametric ones in describingyields. The quality of description of yield classes inthis analysis (which uses injury levels only to defineaxes) varies from adequate (53%) to very good(85%).

Figure 9 leads to a few points:● The figure shows a path of increasing yields,

from very low to high.● No particular injury should be ascribed to

major yield-reducing effects. Rather, combi-nations of injuries should be considered.

● Weed infestation appears to be one importantfactor that determines yield levels. The rela-tionship is not a straightforward one, however.Low weed infestation early in the crop cyclecorresponds to medium-low yields and not tohigh yields. Medium weed infestation cor-responds to high yields. A high weed in-

8. Principal component analysis among some crop growth andinjury variables in upland rice. IRRI, 1998.

festation in the early crop stages correspondsto a range of possible actual yield levels.

This reflects the competition among weedsand the rice crop, and also soil fertility, whichenhances weed emergence. This complexrelationship can also be phrased using the pathof increasing yields. Low weed infestation inthe beginning of the cropping season is notassociated with high yield (and this could beattributable to exhausted soils, for instance).Rather, a link between medium weed in-festation early in the cropping season and highyields is indicated. Weed infestation, itspattern over time, and the succession of weedspecies (not addressed here) might well proveuseful indicators of fertility in the future.

● These domains may also be used for IPMrecommendations. Domain C corresponds tolow yields. It also corresponds to injury levelsthat are usually low. In domain C, therefore,low yields cannot be ascribed to losses due torice pests. Environmental and agronomicfeatures of the rice crop (poor productionsituations) seem rather to be the cause of thelow yields, and there does not seem to be aneed to target any particular pest for IPMunder such production situations. In domain B,corresponding to medium-low yields, mediumweed infestation toward the end of the cropcycle is the only emerging injury. It may bethat this contributes to reducing actual yields.Under production situations that conven-tionally lead to such medium-low yield, weedcontrol in the middle of the crop cycle mightthen be one constraint to consider. Underproduction situations that usually lead to highyields (domain D), weed infestation, bothearly and late in the crop cycle, seem to beconstraints which, when lifted, might lead tohigher yields. It may also be that blast wouldbe a constraint under such production situa-tions. It should be noted, however, that cor-respondence analysis does not specifically linkleaf blast with possible yield reduction. Settinga specific priority on blast should, therefore,be done with caution, and would requirespecific on-farm testing on traditionalvarieties.

1.0

0.5

0.0

-0.5

-1.0-1.0 -0.5 0.0 0.5 1.0

BS1WEED1

WG1

WEED 2 LEAF 2

PANLB1

TILL1LEAF1

DTY1

DTY2

Factor 2

Factor 1


9. Domains of injuries and of potential impact of IPM on upland rice yield from a correspondence analysis. IRRI, 1998.

Upland Rice Research Consortium

The Upland Rice Research Consortium (URRC) fa-cilitates collaboration and cooperation in upland re-search and development among NARS and IRRI.

Progress in 1998

Steering and technical committee meetings were at-tended by 50 NARS, 12 IRRI, and 3 agriculturalresearch organization (ARO) scientists. Site plan-ning meetings, attended by IRRI scientists andNARS researchers were: Vietnam, 22 Feb.; Philip-pines, 26-27 Feb.; Thailand, 4 Mar; Brazil, 14 Mar;India, 26 Mar; Lao PDR, 29-30 Mar; and Indone-sia, 22 Sep. Site work plans were consolidated anddistributed among partners.

Research programs were implemented at sites inthe six full partner countries—India, Indonesia, LaoPDR, Philippines, Thailand, and Vietnam. Therewere 41 collaborative IRRI-NARS experiments:India 13, Indonesia 5, Lao PDR 7, Philippines 2,Thailand 7, and Vietnam 7. Each country site pro-duced a research report that was distributed amongpartners.

Work exchanges, workshops, and on-the-jobtraining activities continued. One IRRI and twoNARS (Vietnam, China) scientists undertook on-the-job training. Four top senior officials from Thai-land visited Vietnam upland sites. Three NARS(Lao PDR, Philippines, and Vietnam) scientists un-dertook training courses on Strategic Research onNutrient Management and one staff member fromThailand attended training on Advanced Experi-mental Design and Data Analysis at IRRI. TwoNARS scientists from Thailand, and one from LaoPDR participated in a Weed Research MethodologyWorkshop at IRRI.

Progress of unreported project

Genetic improvement of upland riceBrigitte Courtois

● Investigated variety × soil × N managementinteractions in root growth under field condi-tions to enhance root development throughproper management. Started modeling nodalroot development to understand systematicallyG × E interactions for root growth in the soilprofile.

Medium yieldsSheath blight;White grubs;No deadhearts;Medium brown spot;(Late)weeds

BSMSHBPW1L

YL

DHA

FO

LBL

WOP

DEFHDEFM

W2L

WHANBA SHRA

F2

BSLWGA

DHH

SHBA

DHLWIH

F1

YM

LBHW2H

DEFL

YH

W1M

BSMSHRP

-0.00740-0.29760-0.58780 0.28280 0.57300-0.87800

NBP

WHP

Neck blast;Whiteheads;Sheath rot;High brown spot

W2M

Low yieldsNo neck blast;Low brown spot;Low (late) weeds;YLL

High yieldsLeaf blast;Low defoliators;Medium brown spot;High (late)weedsMedium (early) weeds

LBA

No leaf blast

B

D

CA

0.3120.2890.2670.2440.2220.1990.1770.1540.1320.1090.0870.0640.0420.019-0.003-0.026-0.048-0.071-0.093-0.116-0.138-0.161-0.183-0.206-0.228-0.251-0.273-0.296-0.318-0.341-0.363-0.386-0.408-0.431-0.453-0.476-0.498

0.3120.2890.2670.2440.2220.1990.1770.1540.1320.1090.0870.0640.0420.019-0.003-0.026-0.048-0.071-0.093-0.116-0.138-0.161-0.183-0.206-0.228-0.251-0.273-0.296-0.318-0.341-0.363-0.386-0.408-0.431-0.453-0.476-0.498


● Developed techniques to apply stress to indi-vidual plots at a specific phenological stage.This system uses drip irrigation with valves oneach plot. Evaluated upland varieties (48entries) differing in maturity for performancewith a 20-d stress period at the vegetative,flowering, and grain-filling stages. Aus varie-ties showed the greatest tolerance for flower-ing stress.

● Evaluated selected lines of a mapping popu-lation under furrow irrigation with two shortstress periods applied near flowering. Identi-fied QTLs associated with grain set understress.

● Evaluated another population of 120 recom-binant inbred lines (RILs) derived from thecross IAC165 × Co 39 for leaf rolling, leafdrying, and relative water content and cropgrowth under water stress. In parallel, mappedthe population using RFLP markers andmicrosatellites and established a pre-liminarymolecular map.

● Evaluated the same population of RILs for itsallelopathic potential under laboratory condi-tions. Located QTLs controlling this trait butdid not find major genes. Advanced themapping populations of RILs specificallydesigned to study the genetic control ofallelopathy up to the F4 generation usingsingle-seed descent.

● Established a collaboration with theUniversity of Mississippi to identify allelo-chemicals and identified extracts with putativeallelochemicals. At least three chemicals, yetto be identified, were found in the extractsusing HPLC.

● Completed the inoculation of a set of 120upland lines from India, Thailand, and thePhilippines with 24 blast isolates. Clusteredthe varieties based on pathotyping and com-pared this dendrogram with the dendrogramresulting from isozyme analyses, whichshowed few relationships. Started probing foranalogues to resistance genes on the samematerial.

● Obtained BC1, BC2, and BC3 generations ofthe crosses needed to transfer QTLs for partialresistance to blast from Moroberekan intoVandana, an elite upland rice variety popularin India, using the advanced backcross QTLanalysis method.

● Broke the linkage between alleles governinghindered endosperm development andrhizome expression in third-generation com-plex hybrids of O. sativa/O. longistaminata,which allowed production of plants withnormal fertility and good rhizome expression.

● Selected 12 individuals from two accessionsof O. longistaminata naturally introgressedwith O. sativa on the basis of non-invasiverhizomes and production ability for assessingthe prospect of domesticating the wild speciesand improving its seed set.

● Evaluated resistance to Meloidogyne grami-nicola (root-knot nematode) for 190 lines ofBCLF1 and BCLF2 mapping populations forfurther gene tagging.

● Implemented the second year of comparisonof breeders’ and farmers’ opinions on uplandvarieties. To test hypotheses on the importanceof grain quality, organized a sensorial evalu-ation of the material showing how farmers’appreciations differ when based on grainquality.

Program outlook

Upland rice ecosystem research will continue toaddress the major constraints in upland systems anddevelop better adapted germplasm and better basicunderstanding of socioeconomic, biotic, and abioticprocesses. Research results will be aimed at devel-opment of more sustainable and productive rice-based cropping systems.

Better understanding of the socioeconomic dy-namics of the uplands led to priority being given tothe dominant rice-based and perennial-based sys-tems, which together cover some 85% of Asian up-land rice area.


Yield stability in upland rice is being developedby enhancing its drought resistance and weed-sup-pressing ability for subsistence systems. Its re-sponse to moderate inputs and its resistance to blastdisease are being enhanced. In resource manage-ment, development of better nutrient, weed, andnematode management technology for favorableareas (where slopes are not steep, or rainfall is reli-able, or both) continues.

The availability of new research technology inecosystem and genetic characterization, the use ofmolecular biology in germplasm improvement andpest and disease characterization, and a long-termapproach to understanding the dynamics of nutri-ents and pests are expected to enable significantgains to be made in the different environments ofthe uplands.

Farmer participation in breeding and selectionprograms is being evaluated. IRRI’s breeding pro-gram now focuses strongly on using new technol-ogy in prebreeding to provide better genetic mate-rial to support the breeding programs of NARS.

Resource management research is developing amore basic understanding of upland processes, in-cluding nutrient cycling, soil acidity, biology ofpests, and erosion. That will underpin the develop-ment of upland systems that have a diversity of riceand other crops.

Economic and policy analysis research will con-tinue to investigate technological, policy, and insti-tutional interventions that enhance food security ofupland farmers and sustainability of upland sys-tems.

The URRC provides a strong framework to fa-cilitate collaborative NARS-IRRI research and in-stitution building in Asia and, through Brazil, inLatin America. The Brazilian production system forupland rice now focuses on favorable areas, with theuse of inputs such as irrigation, fertilizers, andchemical weed and disease control. Farmers areachieving yields of more than 5 t ha-1 and profitabil-ity of around $500 ha-1.

Flood-prone rice ecosystem 71

Research programsFlood-prone rice ecosystem

EFFICIENT SELECTION TECHNIQUES AND NOVEL GERMPLASM FOR INCREASING PRODUCTIVITYOF FLOOD-PRONE RICELANDS 72Rices with high iron and zinc in the grain (PBGB) 72

Optimal growing conditions and mineral content 73Response to nitrogen 73Antinutritional factors 73Improved rice with enhanced iron and zinc in the grain 73Effect of milling on grain iron content 74

Genes/QTLs affecting flood tolerance in rice (PBGB) 74Screening technique for zinc efficiency (SWS) 74Distribution of photoassimilates in deepwater rice (APPA) 75

CROP AND RESOURCE MANAGEMENT TO IMPROVE PRODUCTIVITY AND SUSTAINABILITY OFFLOOD-PRONE RICELANDS 76Kinetics of phosphorus fixation and availability (APPA) 77

Phosphate dynamics in different treatments 78

PROGRAM OUTLOOK 83


Flood-prone rice ecosystem

There are about 12 million ha of flood-prone riceworldwide, with almost 95% of it in South andSoutheast Asia. The flood-prone ecosystem incorpo-rates many types of rice adapted to different floodconditions—deepwater, tidal saline, tidal nonsaline,and boro—grown in widely different environments. Theprogram’s projects, germplasm improvement and cropand resource management, assist national agricul-tural research systems (NARS) in promoting produc-tive, sustainable, rice-based farming systems for theecosystem.

Efficient selection techniques and novelgermplasm for increasing productivity offlood-prone ricelands

Germplasm improvement research continues to fo-cus on abiotic stresses of excess water and problemsoils, and on screening techniques and the geneticsand physiological mechanisms of the predominantstresses in the ecosystem. However, an importantresearch component is identifying and improvingrices with high Fe and Zn in the grain. The projectalso assists NARS in developing improved flood-prone rice cultivars and promotes inter-NARS col-laboration. India and Thailand have assumed lead-ership for production and distribution of deepwaterrice germplasm for South and Southeast Asia.

Rices with high iron and zinc in the grainG.B. Gregorio, D. Senadhira, R.D. Mendoza,A.N.R. Monroy, R.D. Graham,16 R.M. Welch,17 andH.E. Bouis18

Major developments in 1998 were● Identification of a high-Fe content, high-

yielding rice (IR68144-2B-2-2-3) amongimproved lines being tested at IRRI. Progressin establishing the Fe bioavailability in high-density and low-density rice using Fe-deficient rats and human colon (caco-2) cells.

● The discovery of varieties with high Fecontent was made after germplasm screeningshowed that aromatic varieties tended to behigh in Fe content. After milling, they haveabout twice the Fe content of presentcommercial varieties. The significance of thatis that a substantial amount of time is saved bynot having to breed the high-Fe trait into elite


lines. This option remains open, however, forpossibly increasing Fe content by a factorgreater than two.

OPTIMAL GROWING CONDITIONS AND MINERAL

CONTENT

Twenty-three rice varieties, including three com-mercially grown (IR36, IR72, and IR74), weregrown in the greenhouse with optimum nutrients. Fecontent of grain (brown rice) ranged from 10.1 mgkg-1 in IR36 to 26.4 mg kg-1 in Ganjay Roozy(Table 1). Fe was low in all commercial varieties.Zn concentration ranged from 31.4 mg kg-1 in IR36to 58.9 mg kg-1 in Ganjay Roozy. The experimentshowed that there is potential for doubling the Fedensity and increasing the Zn density by 60%.

RESPONSE TO NITROGEN

Three high-yielding rice varieties were tested withfour different levels of added N (0, 46, 90, and 135kg ha-1) in the field and Fe and Zn content of grain(brown rice) analyzed (Table 2). Differences in Feobtained at various N levels were highly significantand indicated that Fe increased with the addition ofN. No significant interaction between N and varie-ties was observed. Zn concentration did not increasewith the addition of N.

ANTINUTRITIONAL FACTORS

In germplasm screening tests for Fe and Zn, a largevariation in P content of brown rice was observed.It ranged from 2.2 to 5.9 g kg-1. All varieties withhigh Fe and Zn also had high P. There were alsovarieties with average Fe and Zn content and highP. From the samples analyzed, 200 were randomly

Table 1. Fe and Zn content of 23 rice varieties grown in agreenhouse with optimum fertility and full protection frominsects and diseases. IRRI, 1998.

Variety Fe (mg kg-1) Zn (mg kg-1)

Ganjay Roozy 26.4 a 58.9 aZuchem 23.4 b 51.0 b-eYR4194 23.2 b 54.0 abcBanjaiman 22.7 bc 53.0 a-dXua Bue Nuo 22.5 bed 46.6 efgIR64446 22.2 bcd 53.5 abcKinmaze 21.7 bcd 51.7 b-fTsuyake 21.2 bcd 42.5 f-iCNA 6187 20.7 bcd 54.5 abMiyazaki 7 20.3 cde 42.5 f-iKetan Ireng 20.2 cde 55.3 abCT7127 20.1 cde 47.0 d-gHuri 370 19.8 de 45.7 efgLagrosa 18.0 ef 48.2 c-fKetan Menah 16.1 fg 45.4 e-hIR10198 15.8 fgh 37.9 ifSkybonnet 15.3 ghi 41.3 ghiIR60864 15.0 ghi 41.1 ghiHeibao 14.9 ghi 31.6 kAlan 14.0 g-i 39.2 hiIR63877 13.1 hij 36.4 ijkIR74 13.0 ij 36.4 ijkIR72 11.7 jk 32.5 jkIR36 10.1 k 31.4 k

chosen and the correlations between P and Fe and Pand Zn content in grain calculated. Highly signifi-cant positive correlations were found for P with Fe(r2 = 0.42) and P with Zn (r2 = 0.50) relationships.The analysis suggests that Fe and Zn content is as-sociated with phytate.

IMPROVED RICE WITH ENHANCED IRON AND

ZINC IN THE GRAIN

High Fe density and high yield traits can be com-bined. This was demonstrated in the cross of IR72and a tall traditional variety from India, ZawaBonday. The line IR68144-3B-2-2-3 from the cross

Table 2. Fe and Zn content (mg kg-1) of three improved rice varieties grown at four levelsof added N. IRRI, 1998.

N level IR60819 IR59682 IR72 Mean(kg ha-1)

Fe Zn Fe Zn Fe Zn Fe Zn

0 12.0c 27.9b 11.4c 25.7b 12.0b 26.5a 11.8c 26.7 45 12.9b 28.5b 12.4b 27.0ab 12.6b 26.5a 12.6b 27.3 90 13.9a 29.8ab 13.4a 28.9a 13.6a 28.4a 13.6a 29.0135 14.2a 30.9a 13.6a 29.0a 13.8a 28.0a 13.6a 29.3 Mean 13.3 29.3 12.7 27.6 13.0 27.3 13.0 28.1


had a high concentration of Fe (21.4 mg kg-1) inbrown rice The elite lines from this cross have goodtolerance for rice tungro virus, are aromatic, andhave excellent grain types. The yields were about10% below IR72 but maturity was earlier. One eliteline is a mid-amylose type suited for rice consum-ers in the Philippines. This elite line will be used forbioavailability feeding trials. It is in the advancedyield trials of the National Seed Industry Council ofthe Philippines.

EFFECT OF MILLING ON GRAIN IRON CONTENT

A comparison at different polishing times of high-Fe traditional varieties demonstrated a strong geno-type × time of milling interaction and indicated thatmuch of the Fe is in the outer layers of the grain.IR64, with the lowest Fe content in brown rice, lostmore than 33% Fe with 15-min polishing but re-mained almost unchanged as polishing time in-creased. A loss of about 33% after 15-min millingwas also observed for the high-Fe traditional ricesJalmagna and Tong Lan Mo Mi, but their Fe con-centrations drastically decreased as polishing timeincreased. A traditional variety from China, XuaBue Nuo, and the high-Fe IR68144-3B-2-2-3 wereless affected by polishing time. With a time equiva-lent to that of commercial polishing (25 min),IR68144-4B-2-2-3 had about 79% more Fe thanIR64 (Fig. 1).

Genes/QTLs affecting flood tolerance in riceK. Sripongpangkul, G.B.T. Posa, D. Senadhira,and Zhikang Li

To facilitate breeding of high-yielding varieties tol-erant of flooding, the genes/QTLs controlling riceelongation ability and submergence tolerance underflooding were investigated using AFLP/RFLPmarkers and 165 recombinant inbred lines (RILs)derived from IR74/Jalmagna (a rapid elongatingrice from India). Under slowly increasing water lev-els, the parents and the RILs were evaluated forelongation ability and submergence tolerance inboth the greenhouse (test 1) and field experiments(test 2).

Five QTLs affecting plant elongation were iden-tified in the IR74/Jalmagna RILs (Table 3). Theseincluded QIne1, QIne2, and QIne4, which affectedinternode and plant elongation. The Jalmagna allele

at QIne1 had a large effect of 13.6 cm and 8.7 cmfor plant and internode elongation in test 1; the re-spective effects in test 2 were 23.2 cm and 18.2 cm.QIne4 was detected only in test 2 and the IR74 al-lele at this locus had a very large effect of 21.8 cmfor elongated internodes. QIne2 was detected in test2 and the Jalmagna allele at this locus caused elon-gated internodes. Two QTLs affecting leaf elonga-tion, QLe6 and QLe7, were also identified. Sevengenomic regions showed significant associationswith submergence tolerance. The Jalmagna allele atfive of these regions was associated with submer-gence tolerance, whereas the IR74 allele at the othertwo regions contributed to submergence tolerance.Four (on chromosomes 1, 3, 4, and 5) of the sevensubmergence tolerance loci were located in the QTLregions for plant elongation. Of these, the markershowing the strongest association with submer-gence tolerance was P2M7-4 on chromosome 9,where a major gene for submergence tolerance,Sub1(t), was reported previously. Surprisingly, itwas the IR74 (non-submergence tolerant parent) al-lele at this locus that contributed strongly to sub-mergence tolerance.

Screening technique for zinc efficiencyP. Thongbai, C.Q. Guerta, and G. Kirk

We seek screening techniques for different types ofZn efficiency in rice:

● external efficiency, allowing greater uptakefrom low-Zn soil; and

1. Grain Fe content of selected rice varieties at differentpolishing times (consumption rice equivalent to 15-minpolishing). IRRI, 1998.

20181614121086420

Xua Bue NuoIR68144IR64JamagnaTong Lan Mo Mi

0 15 30 45 60

Grain Fe content (mg kg-1)

Polishing time (min)


● internal efficiency, allowing greater growthper unit Zn uptake.

Previous work found that rice plants in low-Znsoil were able to solubilize Zn in the rhizosphereand increase their Zn uptake. They did that by acidi-fying the rhizosphere through release of H+ from theroots to balance excess intake of cations over ani-ons, and production of H+ in Fe2+ oxidation by root-released O2. The latter process suggests it might bepossible to screen cultivars for external Zn effi-ciency based on their ability to oxidize therhizosphere.

We compared two cultivars contrasting in exter-nal Zn efficiencies—Madhukar which is efficientand IR26 which is not—for their ability to oxidizethe rhizosphere. The plants were grown in sand thatwas continuously perfused with deoxygenated nu-trient solution. The system was gas-tight so that theonly means of O2 entry was via the roots. We calcu-lated the rates of O2 release from the roots by meas-uring changes in O2 concentration in the solutionbathing the roots.

Figure 2 shows plant growth and root morphol-ogy in the two cultivars. Madhukar produced fourtimes the dry weight of IR26 by the early tilleringstage. Root mass and surface area were larger inMadhukar but not root surface area per unit rootmass. Root porosity and rates of O2 release from the

roots (Fig. 3) were also larger. Oxygen release perpot increased as the plants grew, but rates of releaseper unit root mass decreased, presumably becauseas the root mass increased, the rate of O2 supplyfrom the shoot was increasingly limiting. However,for a given shoot mass, the rate of O2 release perunit root mass was far greater in Madhukar than inIR26. This is consistent with the greater external Znefficiency in Madhukar due to solubilization of soilZn by root-released O2. This method should providea useful screening technique for external Zn effi-ciency.

Distribution of photoassimilates indeepwater riceO. Ito, T. Setter, and A.M. Mazaredo

Deepwater rice (DWR) is grown where maximumfloodwater depth can range from 50 cm to about 400cm. Research has shown that yields of modernDWR were similar to those of high-yielding irri-gated rice grown with the same fertilizer manage-ment (80 kg N ha-1) and agroclimatic environment.This implied that any above-water plant charactersassociated with high-yielding irrigated rice shouldbe applicable for DWR and that the grain-fillingpattern of DWR should not differ from that of high-yielding irrigated rice. An experiment to prove this

Table 3. Main-effect QTLs affecting plant elongation ability and submergence tolerance detected in the IR74/Jalmagna recombinant inbred population.

Test 1 Test 2Traita QTL Chromo- Marker interval

some LOD a (cm) R2 (%) LOD a (cm) R2 (%)

INI QIne1 1 RG109 ~ sd-1 7.0 -8.7 20.1 18.9 -18.2 33.1INI QIne2 2 P2M9-8 ~ P2M6-8 5.1 -9.6 8.6INI QIne4 4 P3M1-5 ~ P3M5-1 10.7 21.8 36.7

LLI QLe4 4 P3M5-1 ~ P2M5-8 6.2 -6.2 14.2LLI QLe6 6 P1M10-7~ P2M5-17 2.5 4.9 9.4LLI QLe7 7 P1M3-9 ~ P1M10-5 3.7 -3.5 12.0

Chromosome Markerb G2 Tolerance allele G2 Tolerance alleleQSut1 1 P1M6-2 23.2 JalmagnaQSut3 3 P1M3-5 15.7 IR74QSut4 4 P2M5-8 19.7 JalmagnaQSut5 5 P1M6-9 7.2 Jalmagna 9.4 JalmagnaQSut8 8 P3M7-3 6.9 Jalmagna 11.9 JalmagnaSub1(t) 9 P2M7-4, 5.1 IR74 58.3 IR74QSut10 10 P3M1-3 13.0 Jalmagna

aINI and LLI are increments of internode and leaf length. The gene effect a is the phenotypic effect due to substitution of the Jalmagna alleleby the IR74 allele. bUnderlined markers are associated with detected QTLs affecting internode or plant elongation. G2 is the likelihood ratiochi-square statistic. The significant values of G2 at P = 0.05, 0.01, and 0.001 are 3.79, 6.63, and 11.60, respectively.


2. Plant growth and changes in root morphology over time in Zn-efficient Madhukar and Zn-inefficient IR26 grown insand continuously perfused with deoxygenated nutrient solution. Means of three replicates; error bars indicate 1 SE.IRRI, 1998.

Days after planting

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point used 14C as a tracer. Flag leaves were fed with14CO2 to compare the photoassimilate partitioningduring the reproductive stage of a modern DWR(HTA60) with that of high-yielding irrigatedcultivars (IR8 and IR72).

The pattern of translocation in irrigated rice wassimilar to that in DWR. The flag leaf assimilateswere translocated quickly to the leaf sheath andeventually stored in the panicle before and afterflowering. At booting, 10 d before flowering, radio-active carbon was localized in the flag leaf, leafsheath, and developing panicle in both DWR andirrigated rice (Fig. 4). No assimilates from the flagleaf were translocated to the lower part of the stemsand adjacent tillers. During grain filling, 10 d afterflowering, 85-93% of assimilates were translocatedimmediately into the panicle (Fig. 5) in all cultivars

48 h after 14C feeding. There was no assimilatetranslocated into the stem in HTA60 and IR8 unlikein IR72 where there were some traces in the stemeven at 24 h after feeding. The research on DWR iscomplete, but the 14C technique developed will beused in research on the sink-source relationship ofthe new plant type (NPT) in the irrigated rice eco-system program.

Crop and resource management toimprove productivity and sustainability offlood-prone ricelands

Research to alleviate constraints to productivity offlood-prone rice, particularly in acidic soils ofcoastal areas, includes analyzing the roles of min-eral elements in flooding tolerance and productiv-


ity of rice cultivars, and developing environmen-tally sound soil and water management. Partner-ships with NARS for formulating and testing newtechnologies to alleviate poverty through promotionof sustainable, higher, and more stable productionsystems are an important part of the flood-prone riceecosystem program.

Kinetics of phosphorus fixation andavailabilityV. P. Singh

Phosphorus is a key nutrient in governing the pro-ductivity potential of soils. Fertilizer P applied tosoil undergoes irreversible sorption and transforma-tions to different forms that strongly influence Pavailability. It is unclear whether P availability iscontrolled strictly by solubility or by sorption rela-tionships. Many soil factors such as pH, quantitiesof Fe, Al, and Ca; type and quantity of clay and or-ganic matter, and level of redox potential are knownto influence P fixation.

Acid sulfate and inland Fe-toxic soils are exten-sively used for crop production in South and South-east Asia, but with poor response to P fertilizationbecause of low pH and high Al and Fe concentra-tions. Leaching and liming are often recommendedto increase P availability. The extent of P fixationand interrelationships of different forms in thesesoils have not been precisely examined. We inves-tigated the kinetics of P fixation and availability inuntreated, limed, and leached acid sulfate soils, and

3. Rates of oxygen release from roots of Zn-efficientMadhukar and Zn-inefficient IR26 into sand culturescontinuously perfused with deoxygenated nutrientsolution. Means of three replicates. IRRI, 1998.

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4. Distribution of 14C in HTA60, IR8, and IR72 at 0, 6, 24, and 48 h afterassimilation of main flag leaf at 10 d before flowering.

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5. Distribution of 14C in HTA60, IR8, and IR72 at 0, 6, 24, and 48 h afterassimilation of main flag leaf at 10 d after flowering.

in inland Fe-toxic and neutral soils. All soils (Table4) were sampled in bulk from undisturbed areas.

The experiment had six treatments: A) untreatedacid sulfate soil without P application, B) untreatedacid sulfate, C) limed acid sulfate, D) leached acidsulfate, E) neutral, and F) inland Fe-toxic soils, allwith P application. For treatments A, B, and C, thesoil was put in five tanks (one tank per replicate) to10 cm thickness. For treatment D, a portion of thesame soil was leached seven times with brackishwater and dried, pulverized, and filled in five tanksto 10 cm thickness. For treatments E and F, the neu-tral soil and inland Fe-toxic soil were separatelyprepared and filled in five tanks in the same manneras treatments A, B, and C. All soils were flooded to5 cm depth with brackish water, and then leveled.

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Table 4. Properties of soils used in a study of kinetics ofP fractions. IRRI, 1998.

Soil Acid sulfate Neutral Inland Fe toxic

Dry pH 3.7 6.5 3.8Organic matter (%) 2.7 1.6 1.0Available P (mg kg-1) 6.8 9.8 6.5Exchangeable Al (mg kg-1) 120 0.7 190Exchangeable Ca (mg kg-1) 2,400 7,880 1,160Active Fe (mg kg-1) 12,000 8,000 2,300Acetate soluble sulfate (mg kg-1) 2,570 94 1,500

After water subsidence, 2.5 t CaCO3 ha-1 wasevenly spread on the soil surface of treatment C. Alltreatments then had 1 t chicken manure ha-1 appliedand were again flooded with brackish water to 3 cmdepth and maintained for 2 wk. Phosphorus wasthen applied as single superphosphate in solutionform at 5 mg P kg-1 soil, followed by a second ap-plication after 2 wk.

Soil samples from each treatment were sepa-rately analyzed before starting the experiment(Table 4), just before P application, and daily for 6d in the first week and once in the second week af-ter P applications. Soil pH, exchangeable Al and Ca,active Fe, and organic matter were determined oncea week.

PHOSPHATE DYNAMICS IN DIFFERENT TREATMENTS

Total phosphate. The trends of total P concentra-tion and its mean values are shown in Table 5 andFigure 6. After P applications, total P content in-creased in all treatments but the increase was sig-nificant only in Fe-toxic soil. The increase waspartly contributed by the addition of brackish water,which contained 0.3 mg total P liter-1.

Iron phosphate. The Fe-P content representedthe most dominant fraction of total P in Fe-toxic soil(23% initial and 28% final mean) and was the low-est fraction in neutral soil (8% and 9%) respectively(Table 5, Fig. 6).


Table 5. Levels (mg kg-1) of total P, iron-P, and aluminum-P in different treatments. IRRI, 1998.a

Total P Fe-P Al-PTreatment

Initialb Finalb Change Initialb Finalb Change Initialb Finalb Change

Untreated acid sulfate without P 129.4 b 131.6 b 2.2 ns 19.8 b 20.0 a 0.2 ns 38.2 a 38.6 c 0.4 nsUntreated acid sulfate with P 129.0 b 131.6 b 2.6 ns 22.0 a 20.0 a -2.0 ** 37.2 a 40.0 b 2.8 **Limed acid sulfate with P 139.8 a 144.2 a 4.4 ns 16.4 c 14.0 b -2.4 ** 38.6 a 42.0 a 2.4 **Leached acid sulfate with P 129.6 b 133.4 b 3.8 ns 11.2 d 12.8 c 1.6 ** 38.2 a 41.8 a 3.6 **Neutral soil with P 137.6 ab 141.8 a 4.2 ns 11.4 d 12.2 d 0.8 ns 0.2 c 0.4 e 0.2 *Iron toxic soil with P 39.2 c 42.8 c 3.6 * 9.0 e 11.8 d 2.8 ** 17.2 b 20.4 d 3.2 **

a* and ** significant at P = 0.01 and 0.05, respectively. bInitial is before P application. Final is the mean of 15 successive samples afterP application.

Before P application, the Fe-P concentrationswere significantly higher in both untreated acidsulfate soils and were lowest in Fe-toxic soil. Theleached and the limed acid sulfate soils had signifi-cantly lower Fe-P concentrations than the untreatedacid sulfate soils. This is attributed to the reductionof ferric Fe due to the removal of acidity and Fethrough leaching, and to the neutralization of acidsand precipitation of Fe compounds with lime. Thelevels of pH and Ca in the soil, and in thesupernatant of both treatments, and pH and Fe con-tent in the leachate of the leached soil support theseexplanations. The decrease in Fe-P was about twotimes more pronounced with leaching than withliming, possibly due to greater soil reduction in theleached soil.

Iron-P concentration increased after P applica-tions for 2 d and then decreased, in all treatments.However, the increase was not significant in theuntreated acid sulfate soil without P and the neutralsoil. These changes were gradual in Fe-toxic andleached acid sulfate soils. The final mean values(Table 5) were identical and significantly higher inboth untreated acid sulfate soils (with and withoutP), and were lower in neutral and Fe-toxic soils.Comparison of final and initial Fe-P values showeddifferent trends in different treatments. There wasno change in untreated acid sulfate soil without Papplication because of the impaired progressive soilreduction due to low soil pH and high active Fe con-centration, which is a more effective oxidant at lowpH. The iron oxides in untreated acid sulfate soilwithout P were X-ray amorphous. No significantchange was noticed in neutral soil, which also hadinherently low Fe content.

Iron-P decreased in limed acid sulfate soil(Table 5), with an overall decrease of 33% due to

soil reduction and consequent precipitation of ironcompounds with lime. The leached acid sulfate soilhad an increase, possibly due to the diffusion of re-duced iron from underneath and its reoxidation atthe soil-water interface. The active Fe retained inthe leached soil has been reported to produce FeSO4and soluble-free Fe upon soil reduction. The oxida-tion of FeSO4 produces Fe(OH)3 precipitate andsoluble H2SO4 and the oxidation of Fe may fix theP present in the system. In this treatment, a continu-ous decrease in water pH and increased levels ofsoluble Fe was also noted. Because of that, the ini-tial decrease of 47% in Fe-P reverted to 39% with a14% increase after P application.

The increase of Fe-P in Fe-toxic soil was attrib-uted to higher levels of active Fe and lower degreeof soil reduction due to low pH, organic matter, andCa contents. These conditions are reported to dimin-ish soil reduction and kinetically favor the forma-tion of Fe-P.

Aluminum phosphate. The Al-P content, aspercentage of total P, was highest in Fe-toxic soil(44% initial and 47% final mean) but lowest(<0.3%) in the neutral soil (Table 5 and Fig. 6). Allacid sulfate soils had almost identical values both atthe initial (29%) and the final stage (30%).

Before P application, all acid sulfate soils hadsimilar, but significantly higher, Al-P concentra-tions than other treatments. The neutral soil had thelowest Al-P concentration. Fe-toxic soil had signifi-cantly lower Al-P content (17.2 mg kg-1) than allacid sulfate soil treatments. The leaching and limingof acid sulfate soil resulted in a significant decreasein exchangeable Al but had no effect on Al-P, ap-parently due to no hydrolysis of Al-bound P.

Al-P concentrations increased after P applicationin all treatments. The increase was consistent in Fe-


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toxic soil, while other soils showed some fluctua-tions. The final mean values were significantlyhigher in limed and leached acid sulfate soils. Theincrease in Al-P over initial values was significantin all treatments except the untreated acid sulfatesoil without P.

Higher concentration and the increase in Al-P inleached and limed acid sulfate soils may have beencaused by the release of Al from the exchange sitesand also from the lattice dissociation of the claymineral. The amorphous and surface activealuminum hydrous oxides (Al (OH)3), formed fromthe neutralization of exchangeable Al, also couldhave contributed to P adsorption. In untreated acidsulfate and in Fe-toxic soils, the Al-P fixation wasessentially due to the Al from exchange sites. Thesetreatments also had significantly higher levels ofexchangeable as well as soluble Al.

The magnitude of change in Al-P, Ca-P, and Fe-P indicates that the presence of Al also enhances therefixation of P released upon the dissolution of Ca-P and the reduction of Fe-P. The increase in Al-P inuntreated acid sulfate soil was closely associatedwith the decrease in Fe-P and Ca-P. In limed acidsulfate soil, it was with applied P and with the de-crease in Fe-P; whereas, in leached acid sulfate soil,it was only with the decrease in Ca-P.

In Fe-toxic soil, the increase in Al-P was mostlyfrom applied P. In that treatment, the levels of ex-changeable Ca and organic matter, as well as soilpH, were too low to cause any significant soil reduc-tion. Hence, decrease in Fe-P, increase in pH, or anyconsequent decrease in Al solubility did not take

place. This treatment had not only the highest con-centration of Al-P and exchangeable-Al but also ofsoluble Al, which could chemically immobilize thesoluble P.

Calcium phosphate. Calcium-P content was thedominant fraction of total P in neutral soil and waslowest in Fe-toxic soil (Table 6 and Fig. 6). Bothuntreated acid sulfate soils also had 35% and 36%initial and 30% and 23% final total P as Ca-P. In thelimed and leached acid sulfate soils, the Ca-P frac-tion was 35% and 46% initially, and 48% and 34%at the end.

Before P application, the Ca-P concentration washighest in neutral soil and was lowest in Fe-toxicsoil. The leached acid sulfate soil had significantlyhigher concentration than other acid sulfate soiltreatments. This was contributed by the brackishwater used for leaching, which contained 0.26 mgliter-1 total P, mostly as Ca-P, and 30 mg liter-1 solu-ble Ca. While Al was being removed through leach-ing, the soluble Ca apparently precipitated P re-leased by the reduction of Fe-P. This is reflected bythe significantly lower initial concentrations of ex-changeable Al and Fe-P without any change in Al-P in this treatment than in untreated acid sulfatesoils.

The Ca-P content in the limed acid sulfate soiltreatment was identical to untreated acid sulfatesoil, but was significantly lower than the leachedacid sulfate soil. That was because of the formationof insoluble Ca complexes with Al and Fe at the soilsurface as a result of their accumulation due to theflooding of soil and evaporation of water prior to

Table 6. Levels (mg kg-1) of calcium P, available P, and supernatant P in different treatments. IRRI, 1998.a

Calcium P Available P Supernatant Pb

TreatmentInitialc Finalc Change Initialc Final c Change Initialc Finalc Change

Untreated acid sulfate 46.2 c 30.4 e -15.8 ** 13.6 b 13.0 c -0.7 ns 0.06 b 0.04 d –0.02 nswithout P

Untreated acid sulfate 45.2 c 49.4 d -5.8 ** 13.6 b 17.4 b 3.8 ** 0.06 b 0.08 bc 0.02 nswith P

Limed acid sulfate 46.4 c 68.8 b 22.4 ** 14.6 a 18.4 a 3.8 ** 0.06 b 0.07 c 0.01 nswith P

Leached acid sulfate 60.0 b 45.2 c -14.8 ** 16.0 a 18.4 a 2.4 ** 0.15 a 0.09 b –0.06 nswith P

Neutral soil with P 105.0 a 113.0 a 8.0 ** 14.0 b 17.8 b 3.8 ** 0.13 ab 0.12 a –0.01 nsIron toxic soil with P 1.5 d 1.0 f -0.5 * 5.8 c 7.8 d 2.0 ** 0.05 b 0.07 c 0.02 ns

a* and ** significant at P = 0.01 and 0.05, respectively. bSum of total and soluble P in water. bInitial is before P application; final is themean of 15 successive samples after P application.


lime application. That was probably because of limeused in inducing soil reduction, which produced fer-rous Fe and neutralized the acidity produced by theoxidation of ferrous Fe. Otherwise the increase inexchangeable Ca and the decrease in Fe-P shouldhave shown an increase in Ca-P, as there was nochange in other P forms, especially the Al-P. Thisexplanation is supported by the subsequent increasein Ca-P and soluble Ca together with the consistentdecrease in soluble Fe and Al. These changes weregreater in limed acid sulfate soil than in leached acidsulfate soil.

The highest initial Ca-P in neutral soil is a char-acteristic of its inherent properties—neutral pH,high Ca, and low Fe and Al content. Likewise, thelowest initial Ca-P in Fe-toxic soil is also due to itsinherent properties: low pH and Ca and high Al andFe levels.

After P applications, different treatments showeddifferent trends of Ca-P. It increased consistently inlimed acid sulfate soil, whereas it decreased in bothuntreated acid sulfate soils. The leached acid sulfateand the neutral soils showed a gradual increase for5 d and a decrease thereafter, while there was prac-tically no change in Fe-toxic soil. The final meanCa-P level was highest in neutral soil, followed bylimed acid sulfate, leached acid sulfate, untreatedacid sulfate with P, untreated acid sulfate without P,and Fe-toxic soil.

The increase in Ca-P in limed acid sulfate soilwas higher than the total amount of applied P, indi-cating also the fixation of P released from the or-ganic fraction. This observation was further sup-ported by the increase in Al-P, which accountedmore than the decrease in Fe-P. The phosphate fixa-tion in this treatment may have been caused by Cafrom lime and from the exchange sites of the soil,and due to P precipitation on the surface of CaCO3particles.

The increase in Ca-P in neutral soil may also betraced to the fixation of P from the organic fractionbecause of the increase in all P forms, which totaledmore than the applied P. This soil contained twiceas much exchangeable and soluble Ca as the limedacid sulfate soil, yet it had lesser increase in Ca-P.The Ca-P increase, amounting to 80% of the appliedP, and a significant increase in available P, indicateCa-P dissolution and nonreactiveness of exchange-

able Ca due to the highly buffered nature of brack-ish water.

The decrease in Ca-P in the untreated andleached acid sulfate soils was possibly caused by itsdissolution due to increased pCO2 during anaerobicdecomposition of organic matter. In these treat-ments, the sum of applied P and the decrease in Ca-P was more than the sum of increase in Al-P andavailable-P, indicating a gain in organic P.

Available phosphate. The trends of available Pconcentrations are shown in Table 6 and Figure 6.Before P application, the leached acid sulfate soilhad the highest level, whereas the Fe-toxic soil hadthe lowest level. In limed acid sulfate soil, it wassignificantly higher than other treatments but simi-lar to the leached acid sulfate soil. Both untreatedacid sulfate soils and the neutral soil had nonsignifi-cant differences. The higher available P in leachedacid sulfate soil was due to the enhanced soil reduc-tion leading to a decrease in Fe-P and lowering ofFe and Al concentrations. Available P, as percent-age of total P, followed the trend of its initial con-tent in all cases except the Fe-toxic soil, whichshowed the highest percentage but had the lowestconcentration.

Available P increased in all P-applied treatmentson the first day and gradually declined after the 4thday. The final mean available P values were highestand identical in both the limed and leached acidsulfate soils. This was followed by neutral soil, un-treated acid sulfate soil with P, and by untreatedacid sulfate soil without P. It was lowest in Fe-toxicsoil (7.8 mg kg-1).

Comparison of final available P values with ini-tial ones showed an increase of 2.0-3.8 mg kg-1—lowest in Fe-toxic soil and highest in the untreatedacid sulfate with P, limed acid sulfate, and the neu-tral soils. In terms of applied P, the increase in thelatter treatments was also largest and identical(38%), whereas in the Fe-toxic soil, it was the low-est (20%).

The increase in available P was generally con-tributed by the applied P and by the decrease in Fe-P and Ca-P levels in all treatments except limed acidsulfate and neutral soils. In the latter treatments, itwas largely contributed by the decrease in organicP fraction, as shown by the higher extent of increasein Al-P and Ca-P than the decrease in Fe-P. Moreo-


ver, there was also an increase in total P in thesetreatments, as noted earlier.

Total fixation of P was high in all the soils stud-ied. Phosphorus application without treating the soilis not rational. With regard to the wide variations inthe intensity of different P-immobilizing pools insoils, different soils warrant different P manage-ment strategies. It is apparent that P fixation cannotbe effectively mitigated in an acid sulfate soil by theconventional rates of lime application. Leachingwith brackish water seems to be highly effective inimproving P availability in this soil as it reduces Pfixation through the removal of acidity, Al and Fe,and enhances soil reduction as well as the dissolu-tion of Ca-P. A lower rate of liming is likely to beeffective as well as economical, if used after leach-ing, which could help soil reduction. Leaching fol-lowed by liming may also be effective in reducingP fixation in Fe-toxic soil.

Program outlook

In flood-prone environments, germplasm improve-ment research will emphasize developing MAStechniques that can increase selection efficiency andpermit simultaneous selection for several traits todeal with abiotic stresses. Mechanism-based screen-ing techniques for P and Zn uptake will be estab-lished and breeding procedures for increasing Feand Zn in grain will likewise be developed.

Research will be continued to determine the re-lationship between soil properties and flooding tol-erance and to assess the environmental impact ofland, water, and crop management practices oncoastal wetlands. Efforts will be made to projectchanges in water resources and land use in coastalareas. Strategies for enhanced sustainability offlood-prone rice lands will be formulated and im-plemented through collaborative partnership withNARS.

Research programsCross-ecosystems research

BIOTECHNOLOGY TOOLS FOR RICEBREEDING 86Molecular markers 86

Use of conserved motifs of disease resistance genesto characterize elite genetic stocks andgermplasm (PBGB, EPP) 86

Physical mapping of bacterial blight resistance genexa13 (PBGB) 88

Improved resistance of new plant type lines tobacterial blight by marker-aided transfer ofresistance genes (PBGB) 88

New models and computer software for mappingQTLs involved in epistasis and G×E interactions(PBGB) 90

Physical mapping of the rice genome using IR64library (PBGB) 91

DNA markers and salinity tolerance in rice(PBGB) 91

Tagging of gall midge resistance genes (PBGB) 93Wide hybridization 94

Production of interspecific hybrids and backcrossprogenies (PBGB) 94

Characterization of wide-cross derivatives throughin situ hybridization (PBGB) 94

AFLP analysis of Oryza species (PBGB) 95Rice transformation 96

Effectiveness of PEPC promoter in Bt rice (EPP) 96Transgenic approaches to tungro virus (EPP) 96

Organization of the International Molecular BreedingProgram (IMBP) 97

EXPLOITING BIODIVERSITY FOR SUSTAINABLEPEST MANAGEMENT 97DNA sequence variation in rice tungro viruses 97

Resistance-breaking mechanism inRTSV-Vt6-TKM6 (EPP) 97

Differential reactions of RTBV variants (EPP) 98IR64 deletion mutants for functional genomics

(EPP) 98Bacteria with disease antagonism and plant growth-

promoting properties (EPP) 100

Heritability of Bt tolerance in the striped stem borer(EPP) 100

Invertebrate biodiversity in a Philippine farmer's field(EPP) 102

Effect of water management on sheath blight spread(EPP) 102

ASSESSING OPPORTUNITIES FOR N2 FIXATION

IN RICE 105Homologues of legume ENOD genes in rice (SWS,

PBGB) 105Characterization of the homologues of legume ENOD93

from rice (SWS, PBGB) 105Ability of rice to perceive rhizobial nod factors

(SWS, PBGB) 107

IMPLEMENTING ECOREGIONAL APPROACHESTO IMPROVE NATURAL RESOURCEMANAGEMENT IN ASIA 109Characterization of tropical lowland rice production

situations and injury profiles 109Characterization: production situations and injury

profiles (EPP) 109A multiple-pest, production situation-specific model to

simulate yield losses of rice in tropical Asia 113Model structure (EPP) 113Model calibration and testing (EPP) 114

The Systems Research Network (SysNet) forecoregional land use planning 116The SYSNET methodology (APPA, EPP) 116

PROGRESS OF UNREPORTED PROJECTS 119Rice — a way of life for the next generation of rice

farmers (APPA, AE, SS, CREMNET) 119Socioeconomic studies for technology impact,

gender, and policy analysis(SS, EPP, APPA) 120

PROGRAM OUTLOOK 120


Cross-ecosystems research

The goal of the Cross-ecosystems Research Programis to acquire and develop knowledge and tools for useby ecosystem-based research programs at IRRI and innational agricultural research systems (NARS), and toaddress current or anticipated problems common toall ecosystems. The research conducted under theProgram cuts across disciplines and ecosystems.

The program builds on rapid advances in molecularbiology, knowledge of evolving rice pests, alternativeapproaches to natural resource management forrelatively homogeneous agroecoregions, understand-ing farmers’ current knowledge and factors affectingthe absorption of scientific knowledge, assessingfarmers’ need of technologies in the context ofemerging trends in the rice sector of the economy,and evaluating the impact of technologies on the well-being of the people.

The Program consists of the following six projects:1. Applying biotechnology to accelerate rice

breeding and broaden the rice genepool2. Exploiting biodiversity for sustainable pest

management3. Biological nitrogen fixation4. Rice: a way of life for the next generation of rice

farmers5. Socioeconomic studies for technology impact,

gender, and policy analysis6. Implementing ecoregional approaches to

improve natural resource management in AsiaThe Program is the home of the Asian Rice

Biotechnology Network (ARBN) and continues toprovide technical support to NARS scientists involvedin the network on Systems Analysis and Simulationsin Rice Production Systems (SysNet).

Biotechnology tools for rice breeding

Biotechnology tools can increase the efficiency andscope of rice breeding and broaden the genepool ofvaluable traits. The tools include DNA marker tech-nology, DNA fingerprinting, anther culture, widehybridization, and transformation.

Significant advances in the development and useof biotechnology since 1988 have solved difficultproblems in rice improvement. Since 1993, theARBN has promoted collaborative research be-tween NARS and presented training courses in bio-technology techniques and their applications.

The application of biotechnology tools at IRRIand at NARS institutes continues, with new ap-proaches and new standards of performance helpingto increase the power of the biotechnology ap-proach.

Molecular markers

USE OF CONSERVED MOTIFS OF DISEASE

RESISTANCE GENES TO CHARACTERIZE ELITE

GENETIC STOCKS AND GERMPLASM

H. Leung, M. Bernardo, L. Ebron, H. Tsunematsu,H. Kato, T. Imbe, L.T. Nghia,28 and V.D. Quang28

A new series of blast-resistant, near-isogenic linesin IR24 background (IR24 NILs) were establishedfor evaluating the performance of individual genes,characterizing pathogen populations, map-basedcloning, and construction of gene pyramids. Resist-ance gene analog (RGA) markers were applied tocharacterize those elite genetic stocks and to tag re-sistance genes by cosegregation analysis.

Cross-ecosystems research 87

We used polymerase chain reaction (PCR) prim-ers corresponding to the leucine-rich repeats (LRR),nucleotide binding sites (NBS), and kinase domainsof disease-resistance genes to fingerprint IR24 NILscarrying nine blast resistance genes (Pi) (Table 1).Because the PCR markers correspond to conservedmotifs of disease-resistance genes, any unique dif-ferences between the lines serve not only as diag-nostic markers for IR24 NILs, but represent poten-tial markers linked to specific resistance genes.Those markers can be used for marker-aided selec-tion (MAS) in the development of elite lines andcultivars.

DNA was extracted from homozygous resistant(RR) and homozygous susceptible (ss) lines fromBC6F3 populations from different cross combina-tions carrying specific Pi genes. Four primer pairsdetecting resistance-gene analogs were used to am-

plify polymorphic DNA fragments of IR24 NILs.DNA amplification was performed using 45 °C an-nealing temperature and amplified products weresubjected to electrophoresis using 4.0% polyacryla-mide gels. The products were detected using silverstaining.

The background of all IR24 NILs was nearlyidentical (>90% similarity in banding patterns) in-dicating genetic homogeneity of the backcrosspopulations. Diagnostic RGA markers for Pi-3,Pi-i and Pi-7 genes were detected providing uniqueDNA fingerprints for individual NILs (Fig. 1). RGApolymorphic markers were also detected among re-sistant and susceptible families in advanced back-cross populations. Figure 2 illustrates the cosegre-gation between a RGA marker produced by NBSprimers and Pi-i gene. Two potentially linked mark-ers were also detected in Pi-i and Pi-z5 genes usingNBS primers.

The markers cosegregating with Pi genes couldbe candidate resistance genes or part of the geneclusters containing the conserved motifs. Experi-ments are under way to tag additional resistancegenes in IR24 NILs using RGA markers. We arecloning the RGA markers linked to Pi-i and Pi-z5

resistance genes. Sequence-tagged site (STS) prim-ers will be designed from these RGA markers toimplement MAS.

In addition to gene tagging in NILs, the RGA ap-proach is widely used to assess functional diversityof disease-resistance germplasm. Donor parents and

Table 1. Blast resistance genes in IR24 NILs available fortagging with resistance gene analog markers. IRRI, 1998.

Donor Resistance Diagnostic fungalgene isolate

Fujisaka 5 Pi-i PO6-6Kasabue Pi-k PO6-6Pi no. 4 Pi ta-2 IK81-3C101LAC Pi-1 PO6-6C101PKT Pi-ta IK81-3C104PKT Pi-3 PO6-6/PO3-82-51C101A51 Pi-z5 PO6-6/IK81-3WHD-IS-75-1-127 Pi-9(t) PO6-6RIL 29 Pi-7(t) PO6-6

1. DNA fingerprint of IR24 NILs showing uniform background. A diagnostic band for Pi-3 gene was detected by XLRR RGA primer.IRRI, 1998.

Pi-1 Pita-2 Pi-1 Pi-3 Pi-5 Pi-9 (t) IR24 Pi-k Pi-1 Pi-ta IR24


2. A RGA marker S1/As3 that cosegregates with Pi-i gene. IRRI,1998.

Fujisaka 5 IR24 RR ss Fujisaka 5 IR24

commercial varieties from Vietnam, Nepal, andcentral and southern China were fingerprinted usingRGA markers (Fig. 3). Our results show that withthree representative primers corresponding to theconserved motifs of LRR, NBS, and kinase do-mains, we can reliably determine the genetic rela-tionships among donor and commercial varieties.This provides an efficient tool to track the pedigreesof elite germplasm and may eventually lead to ac-curate prediction of functional resistance based onRGA polymorphic markers.

PHYSICAL MAPPING OF BACTERIAL BLIGHT

RESISTANCE GENE xa13A.C. Sanchez, L. Ilag,29 D. Yang, D.S. Brar,F. Ausubel,30 G.S. Khush, M.Yano,27 T. Sasaki,27

N. Huang, and Z. Li

The recessive gene, xa13, confers resistance to Phil-ippine race 6 (PXO 99) of the bacterial blight (BB)pathogen Xanthomonas oryzae pv. oryzae (Xoo).Fine genetic mapping and physical mapping usingthe map-based cloning approach were conducted asinitial steps in an effort to isolate the gene. Usingnine selected DNA markers and F2 populations of132 and 230 plants, xa13 was fine-mapped in a ge-nomic region <4 cM on the long arm of rice chro-mosome 8, flanked by two restriction fragmentlength polymorphism (RFLP) markers, RG136 andR2027. Four DNA markers (RG136, R2027,S14003, and G1149) in the target region were usedto identify bacterial artificial chromosome (BAC)clones potentially harboring the xa13 locus from arice BAC library. Eleven BAC were identified,forming four separate contigs including a singleclone contig, 29I3 associated with the RG136 STSmarker, the S14003 contig consisting of four clones

(44F8, 41O2, 12A16, and 12F20), the G1149 contigof two clones 23D11 and 21H18, and the R2027contig consisting of four overlap clones 42C23,30B5, 6B7, and 21H14. Genetic mapping indicatedthat the xa13 locus was contained in the R2027contig. Chromosomal walking on the R2027 contigresulted in clones 33C7 and 14L3. DNA fingerprint-ing showed that the six clones of the R2027 contigwere overlapping. Clone 14L3 hybridized with asingle fragment from the clone 44F8, integrating theR2027 and S14003 contigs into a single contig con-sisting of 10 BAC clones with a total size of ~330kb.

The physical presence of the xa13 locus in thecontig was determined by mapping the ends of theBAC inserts generated by TAIL-PCR. In an F2population of 230 plants, the BAC-end markers42C23R and 6B7F flank the xa13 locus. The probes21H14F and 21H14R derived from BAC clone21H14 were found to flank xa13 at a distance of 0.5cM on either side (Fig. 4). Thus, genetic mappingindicated that the contig and the 96-kb clone 21H14contained the xa13 locus. Further efforts to isolatexa13, including construction of the xa13 cDNA li-brary, identification of the resistant allele at xa13,subcloning of clone 21H14, and genetic comple-mentation, are under way.

IMPROVED RESISTANCE OF NEW PLANT TYPE LINES

TO BACTERIAL BLIGHT BY MARKER-AIDED

TRANSFER OF RESISTANCE GENES

A.C. Sanchez, D.S. Brar, N. Huang, Z. Li, andG.S. Khush

IR65598-112-1 and the two sister lines, IR65600-42and IR65600-96-28, are promising new plant type(NPT) lines with high yield potential. However,they are susceptible to BB caused by Xoo. To im-prove the resistance of the NPT lines to Xoo, threeBB resistance genes (xa5, xa13, and Xa21) weretransferred to them via marker-aided backcrossing.STS markers for the three target resistance geneswere developed based on DNA sequences of the tar-get gene (Xa21) or of their linked RFLP markers(RG556 and RG207 for xa5 and RG136 for xa13).Marker polymorphism for xa13 was detected afterdigestion of the PCR products with HinfI enzyme.

Fifty-nine BC3F3 NILs in the three NPT back-grounds containing one to three BB resistance genesin various combinations were developed through


MAS for the resistance genes and phenotypic selec-tion for the NPT phenotype. While showing a widerresistance spectrum, the BC3F3 NILs having morethan one BB resistance gene manifested increasedlevels of resistance to the Xoo races, compared withthose having a single BB resistance gene (Table 2).

Our results, based on two F2 populations and theprogeny testing of their F3 lines, showed that MASrespectively reached the accuracy of 95% and

95.8% of identifying homozygous resistant plantsfor xa5 and xa13. These NPT NILs for BB resist-ance genes provided valuable breeding materials forbreeding and genetic study of the relationship be-tween rice plants and Xoo. Our results demonstratedthe usefulness and efficiency of MAS in genepyramiding and the strategy of developing PCR-based polymorphic markers for MAS in rice im-provement.

3. Central Vietnam rice varieties fingerprinted by RGA markers. The dendrogram is generated using GelCompar software. The scaleindicates percent similarity between groups. The varietal groupings with different spectra of blast resistance are consistent with thegenetic relationships expected from known pedigrees. Duplicated names are accessions. IRRI, 1998.

IR36

CN2

CL-88-66

LC-88-66

K13

Heo ran

MTL61

Chiem

Chiem rau

Bat

Nep ran

Nep sao vang

Nep sao vang

Nep da nang

MT58

C61MT

Song hy

Lua thom

Heo ran

Ba trang

CN2

CN2

Nep thom

Nep thom

DH7

Nep

CR203

IR66

MT61

Chiem

Nep chiem

Nep chiem

DC1

Nep ma

25 Cu ba

40 50 60 70 80 90 100


NEW MODELS AND COMPUTER SOFTWARE FOR

MAPPING QTLS INVOLVED IN EPISTASIS AND G × E

INTERACTIONS

D.L. Wang,3 J. Zhu,3 Z. Li, and A.H. Paterson24

A new methodology based on mixed linear modelswas developed for mapping quantitative trait loci(QTL) with digenic epistasis and QTL × environ-ment (QE) interactions. A two-dimensional searchand the control of background genetic variationwere applied in the mixed model approaches. Reli-able estimates of QTL effects (additive effects and

epistasis effects) can be obtained by maximum like-lihood estimation, while QE interaction effects (ad-ditive × environment interactions and epistasis × en-vironment interactions) can be predicted by the bestlinear unbiased prediction method. Likelihood ratioand t statistics were combined for testing hypoth-eses about QTL effects and QE interactions. MonteCarlo simulations were conducted for evaluating theunbiasedness, accuracy, and power for parameterestimation in QTL mapping. The results indicatedthat the mixed model approaches could provide un-biased estimates for positions and effects of QTLs,

4. Alignment of genetic and physical maps of xa13. The physical map is shown as overlapping BAC clones represented as solid linelength equal to the insert size as estimated through pulse field gel electrophoresis. Numbers in parenthesis after clone names are insertsize in kb. The genetic map is shown as genetic distance in cM. a) Genetic map derived from the NPT population; b) Genetic map usingthe NIL population; c) Genetic map from the Nipponbare/Kasalath mapping population. IRRI, 1998.

Table 2. Reactions of NPT BC3F3 lines to six Philippine races of bacterial blight pathogen, Xanthomonas oryzae pv.oryzae. IRRI, 1998.

Recurrent parent Target gene Race 1 Race 2 Race 3 Race 4 Race 5 Race 6PXO 611 PXO 85 PXO 79 PXO 71 PXO 112 PXO 99

IR65598-112-1 xa5 R R R MR R S-2 xa13 S S S S S R-3 Xa21 R R R R R R-4 xa5/xa13 R MR MR R MR R-5 xa5/Xa21 R R R R R R-7 xa13/Xa21 R R R R R R-10 xa5/xa13/Xa21 R R R R R RIR65600-96-28 xa5 R R R MR MR S-17 xa13 S S S S S R-18 Xa21 R R R R R R-19 xa5/xa13 R R R R R MR-20 xa5/Xa21 R R R R R R-22 xa13/Xa21 R R R R R R-24 xa5/xa13/Xa21 R R R R R R

41O2 (53)12F20 (51)12A16 (46)

44F8 (138)

42C23 (68)30B5 (50)

6B7 (64)FF21H14 (96)

14L3 (94)33C7 (54)R F

R

R

42C23R xa13 - R2027 6B7F

21H14R 21H14F

1.2 1.0 0.8

0.5 0.5 0.5

1.9

3.3

S14003

a

b

c


as well as unbiased predicted values for QE interac-tions. The mixed model approach also showed highaccuracy and power in mapping QTLs with epistaticeffects and QE interactions. Based on the modelsand methodology, computer software (QTLMapperversion 1.0) was developed, which is suitable forinterval mapping QTLs with epistatic effects andQE interactions in DH, RI, and BC populations.This work was accomplished through collaborationwith Zhejiang University, China, and Texas A&MUniversity, USA.

PHYSICAL MAPPING OF THE RICE GENOME USING

IR64 LIBRARY

A.C. Sanchez, B. Fu, J. Domingo, J. Talag, G.Posa, D. Yang, R. Maghirang, L.T. Nguyen, D.S.Brar, J. Bennett, G.S. Khush, and Z. Li

Construction of a physical map of the rice genomeusing the IR64 BAC library is in progress. We es-tablished the backbone of the IR64 physical mapwith 378 anchor islands (contigs) consisting of1,100 BAC clones identified by anchor DNA mark-ers. We also established 350 random BAC islandsconsisting of more than 1000 BAC clones. The cur-rent physical contigs covered about 20% of the ricegenome with more than 50% coverage for chromo-some 11 and more than 30% for chromosomes 12and 3.

DNA MARKERS AND SALINITY TOLERANCE IN RICE

G. Gregorio, B. Ghareyazie, Z. Li, J. Bennett, andD. Senadhira

Marker-aided selection development for salinitytolerance in rice. MAS for salinity tolerance wouldaccelerate breeding progress by increasing selectionefficiency. Tagging these genes for salinity toler-ance is the first step in developing the PCR-basedmolecular markers. Amplified fragment lengthpolymorphism (AFLP) mapping generated rapid,numerous, reproducible, and dominant markers.Although an F8 recombinant inbred population(IR66946) developed from indica parents (IR29, asalt-sensitive improved variety/ Pokkali, a toleranttraditional variety) was used, 206 AFLP markerswere generated using 32 primer combinations. TheAFLP markers were able to construct a linkage mapof all 12 chromosomes and were used in taggingsalinity tolerance.

Salinity tolerance gene tagged. With the use ofthe phenotypic marker for salinity tolerance (saltol),marker analysis mapped the gene between flankingAFLP markers P3/M9-8 and P1/M9-3. Distanceswere respectively 14.7 cM and 18.6 cM. The saltolgene was in chromosome 1 with LOD 5.7. The lo-cation of the saltol gene in this study may be thesame as that of the SalT gene in the Cornell map,which contains an open reading frame coding for aprotein of 140 amino acid residues. SalT mRNA ac-cumulates rapidly in sheaths and roots of matureplants and seedlings after treatment with Murashigeand Skoog salts. The organ-specific response of saltis correlated with the pattern of Na accumulationduring salt stress.

QTLs for salinity tolerance mapped. A quan-titative measure of the Na and K concentrations, andNa-K ratio absorption in the shoot at seedling stagein salinized conditions, was taken from each line inthe population. Marker analysis was performed onlyon RILs in the extreme tails of the distribution, i.e.,those with the lowest and highest value for Na andK concentrations, and Na-K ratio. Any allele fre-quency at any AFLP marker locus differing signifi-cantly at P<0.001 between the two extreme sub-populations was inferred as the location of a salin-ity tolerance QTL.

Based on interval analysis where sets of linkedmarkers were analyzed simultaneously with regardto their effect on the quantitative traits (Na, K, andNa-K ratio), three QTLs were detected for K ab-sorption, four for Na absorption, and three for Na-K ratio. These include the major gene saltol in chro-mosome 1. The QTLs detected for K absorption, inaddition to the major gene in chromosome 1, werelocated in chromosomes 4 and 12 with 83.5% and21.2% of the total phenotypic variation explained(Table 3). For Na absorption, QTLs were detectedin chromosomes 1 and 10 and two in chromosome3,. and respectively explained 64.6%, 35.6%,17.1%, and 16.0% of the phenotypic variation (Ta-ble 3). For Na-K ratio, the three QTLs were locatedin chromosomes 1, 10, and 12 which respectivelyexplained phenotypic variations of 64.3%, 86.1%,and 18.5%.

A common QTL was observed in chromosome 1for the three quantitative traits (low Na, high K, andlow Na-K ratio) putatively associated with salinitytolerance. This segment in chromosome 1 containedthe saltol gene which explained a range of 64.3-


80.2% of the total phenotypic variation with LOD>14.5. A common QTL was also detected on chro-mosome 12 for traits Na and Na-K ratio, which re-spectively explained 21.2% and 18.5% of thephenotypic variation and LOD of 3.46 and 3.14.

Fine mapping the salinity tolerance gene. Finemapping involves the saturation of the chromosomeregion with molecular markers where the salinitytolerance gene was detected and the use of largerpopulation size to approximate the true linkagevalue of the molecular markers and the gene. The275 F8 RILs were phenotyped for salinity tolerancein a controlled environment in the IRRI phytotron.The phenotyping was done by two separate experi-ments. First was the visual reaction of the RILs tosalinity using the modified standard evaluation sys-tem, and the other was the absorption of Na and Kand Na-K absorption ratio in the shoot. The mecha-nism for salinity tolerance in rice is the ability toabsorb less Na+ and take up more K+ to maintain agood Na-K balance in the shoot. The screening testswere maintained at 29/21 °C day/night temperature,a minimum relative humidity of 70% during the dayand natural daylight. Final phenotyping will be in anaturally saline field in Iloilo Province, Philippines.

STS markers near the salinity tolerance genewere used for a parental survey. Of the 32 STSmarkers surveyed in chromosome 1, only 7 werepolymorphic even after 20 restriction enzyme diges-tions. Genotyping the 275 F8 RIL populations withpolymorphic STS markers will be continued andmicrosatellite markers will also be used to saturatethe region containing the salinity tolerance gene.

Salt tolerance in Pokkali. The Indian land racePokkali has been frequently used as a donor of sa-linity tolerance in rice breeding. The salt toleranceof Pokkali is related to its capacity to maintain ahigh K-Na ratio in the shoot. The factors modulat-ing this ratio are not understood at the physiologi-cal, cellular, or molecular levels.

The recent discovery of a wheat gene, hkt1, en-coding a high-affinity K transporter, provided anentry point into the molecular study of salt tolerancein Pokkali. This approach was given additional im-petus when a mutant form of wheat hkt1 was re-ported to confer salinity tolerance in yeast. Wefound that marker RZ405 on chromosome 6 of therice genetic map had high sequence homology withwheat hkt1. We used PCR to amplify part of thehkt1 locus from both Pokkali and IR29, a salt-sensi-tive cultivar. When the two amplicons proved to beof the same size, we used more than 30 randomlyselected restriction endonucleases in an unsuccess-ful attempt to find a polymorphism betweenamplicons.

After the approach of randomly choosing restric-tion endonucleases failed, we isolated the entirehkt1 gene from an IR36 λ genomic library and usedthe sequence information to amplify the entire genefrom Pokkali and IR29. We found a small numberof single-base differences between the Pokkali andIR29 alleles, including one that was detectablethrough use of the restriction endonuclease NdeI.

Digestion of the IR29 and Pokkali ampliconsconfirmed that NdeI was able to detect a polymor-phism between the alleles. We then used this en-zyme to examine the segregation of the IR29 andPokkali alleles in an F8 mapping population derivedfrom IR29/Pokkali. We examined 40 lines (from apopulation of 277 RILs) that were at least as salt-sensitive as IR29 and 40 lines that were at least assalt-tolerant as Pokkali. All 80 RILs contained onlythe Pokkali allele, a total bias against the IR29 al-lele. No DNA marker at any other locus showedcomparable bias. Other DNA markers on chromo-some 6 showed quite balanced distributions of IR29and Pokkali alleles among the 80 lines. Further-more, the waxy locus on chromosome 6 showedunbiased segregation.

We concluded that the Pokkali allele at the hkt1locus makes little or no contribution to the salt tol-erance of Pokkali. However, it competes so strong-

Table 3. QTLs identified by interval analysis for K and Naabsorption and Na-K ratio in the shoot. IRRI, 1998.

Index Marker interval Chromosome no. LOD

K absorption195-209 P3/M9-8 - Saltol 1 17.2206-200 RG375 - P4/M3-2 4 5.33 - 93 P1/M1-3 - P2/M1-3 12 3.4

Na absorption195-209 P3/M9-8 - Saltol 1 14.539 -188 P1/M5-3 - P3/M9-1 3 3.288 -67 P1/M10-6 - P1/m7-10 3 3.027 -25 P1/M3-10 - P1/M3-8 10 4.0

Na-K ratio195-209 P3/M9-8 - Saltol 1 14.5207-65 G291 - P1/M7-8 10 3.63 - 93 P1/M1-3 - P2/M1-3 12 3.1


ly against the IR29 allele at some stage in plantgrowth that no copy of the IR29 allele survives.

All but one of the point mutations distinguishingthe hkt1 alleles of IR29 and Pokkali appear to betrivial. The exception is the mutation that created ordestroyed the NdeI site mentioned above. The mu-tation is actually a frame-shift mutation that is pre-dicted to alter the last 60 of the ~510 amino acids ofthe transporter protein. The IR29 protein is pre-dicted to contain 30 amino acids fewer than thePokkali allele as a result of early translational ter-mination. Such a mutation may not be lethal in it-self and could survive in the homozygous state (asin IR29) but it may be sufficiently deleterious thatit could be at a severe disadvantage relative to thePokkali allele. However, we cannot eliminate thepossibility that the loss of the IR29 allele of hkt1 isnot due to the locus itself but to a closely linked lo-cus.

We examined the pedigree of IR29 and askedIRRI’s Genetic Resources Center for stored seeds.PCR and NdeI digestion traced the abnormal alleleback to Peta, one of the most commonly usedcultivars in IRRI’s breeding program. The absenceof the Peta allele from most of the IR cultivars de-rived from Peta confirms that the allele is associatedwith a very unfavorable phenotype.

TAGGING OF GALL MIDGE RESISTANCE GENES

S.K. Katiyar,31 B.C. Huang,32 and J. Bennett

The Asian rice gall midge Orseolia oryzae is themost important dipteran pest of rice. It is most com-monly found in eastern, central, and southern India;in the wet zone of Sri Lanka; and in southern China.Breeding for resistance to gall midge has been hin-dered by the existence of many biotypes of the in-sect. IRRI and several collaborating NARS insti-

tutes in Asia have used molecular tools to 1) tag sev-eral of the resistance genes for use in DNA MASand 2) provide insight into the biodiversity of theinsect.

Tagging is accomplished by bulked segregantanalysis, usually of the F3 or F4 generation of a crossbetween a gall-midge-resistant cultivar and a sensi-tive cultivar. Wherever possible, the sensitivecultivar is an elite cultivar into which gall midgeresistance must be introgressed. The F3 or F4 popu-lation is phenotyped for gall midge resistance in thegreenhouse or field and at least 40 lines that aretrue-breeding for resistance or true-breeding forsusceptibility are identified. DNA is extracted fromthe 80 lines and from the two parents for amplifica-tion by random amplified polymorphic DNA(RAPD) analysis. RAPD bands that are found in theresistant parent and the resistant lines but are absentfrom the susceptible parent and the susceptible linesare noted, as are bands with the opposite pattern ofappearance. These bands are cloned and mapped,and either used as markers for the resistance genesor as pointers to the location of even closer mark-ers.

This approach was used successfully to tag theGm2, gm3, Gm4, Gm5, and Gm6 genes. MAS kitswere developed for Gm2 and Gm6 and were underdevelopment for gm3, Gm4, and Gm5 (Table 4).Assam land race ARC5984 contains the Gm5 genethat is effective in India and probably another gene(Gm?) that is effective in China. The mappingpopulation used to map Gm5 will be used in 1999to map the Gm? gene.

Because gall midge resistance is occasionallyovercome by changes in the gall midge population,the goal is to pyramid two or more resistance genesin key elite cultivars. In southern China, the goal isto move both Gm6 and Gm? into hybrid rice by per-

Table 4. Use of marker-aided selection (MAS) for rapid generation of near-isogenic linesfor gall midge resistance in elite backgrounds. IRRI, 1998.

Gene Donor Status of MAS Targeted cultivars (recurrent parents)

Gm1 W1293 Mapping population Kranti, Swarna in IndiaGm2 Phalguna Gene mapped Kranti, Swarna in Indiagm3 RP2068 Gene tagged Kranti, Swarna in IndiaGm4 Abhaya Gene mapped Kranti, Swarna in IndiaGm5 ARC5984 Gene tagged Restorers for hybrid rice in ChinaGm6 Duokang #1 Gene mapped Restorers for hybrid rice in ChinaGm? IR36 Tagging in progress Sri Lankan cultivars


forming MAS on key restorer or maintainer lines.In India, the goal is to pyramid Gm2 and Gm4, andlater gm3 and Gm5, into elite inbred lines of therainfed lowlands of eastern and central states andhybrid rice grown in southern states.

Gm6 is effective against all four gall midgebiotypes known in China but is ineffective againstany of the biotypes of India, Nepal, and Sri Lanka.This result is consistent with the result of DNA fin-gerprinting of gall midge isolates in those countries.DNA fingerprinting, accomplished by AFLP analy-sis, revealed that the gall midge of China, Laos, andthe northeast Indian state of Manipur are closely re-lated among themselves but only distantly related togall midge of the rest of the Indian subcontinent,which are closely related among themselves. Thereappears to be two species or subspecies of gallmidge in Asia, instead of one as previously be-lieved. This information is of crucial importance inplanning where new resistance genes should besought and where they should be deployed.

Wide hybridization

PRODUCTION OF INTERSPECIFIC HYBRIDS AND

BACKCROSS PROGENIES

D.S. Brar, R. McNally, J. Molinawe, G.S. Khush,and M. Jones33

An IRRI-West Africa Rice Development Associa-tion (WARDA) collaborative project, InterspecificHybridization between African and Asian Rice Spe-cies, seeks to 1) transfer resistance to African ricegall midge (ARGM) and rice yellow mottle virus(RYMV) and tolerance for abiotic stresses andweed competitiveness from O. glaberrima to high-yielding indica cultivars of O. sativa. Seeds of 18accessions of O. glaberrima were received fromWARDA. Some of those had been identified as re-sistant to ARGM and RYMV and as possessingweed competitiveness. Preliminary screening atIRRI showed a few accessions having increased tol-erance for nematodes (Meloidogyne graminicola),Fe toxicity, Al toxicity, and P deficiency.

Hybrids were produced with IR64 and BG90-2and O. glaberrima accessions TOG 5674, 5675,5681, 5697, 5860, 6216, 6472, 6508, 6589, 6629,6631, 7235 and 7291. The hybrids were highly ster-ile and were backcrossed using BG90-2 and IR64 asrecurrent parents. The BC1F1 were also highly ster-

ile and set only a few seeds upon selfing. Back-crossing subsequently produced more than 3,000backcross (BC2/BC3) progenies. Those progenieswill be evaluated at WARDA and IRRI for differ-ent target traits and at IRRI for the possible intro-gression of genes from O. glaberrima into O. sativa.

CHARACTERIZATION OF WIDE-CROSS DERIVATIVES

THROUGH IN SITU HYBRIDIZATION

F. Abbasi, M. Ashgar, J. Talag, D. S. Brar, K.Fukui,34 and Z. Li

A series of hybrids from crosses of cultivated riceand various wild species, representing BBCC, CC,CCDD, EE, FF, GG, and HHJJ genomes, have beenproduced. In addition, monosomic alien additionlines (MAALs) and introgression lines derived fromvarious crosses involving cultivated and wild spe-cies are also available. We used genomic in situ hy-bridization (GISH) to characterize parental chromo-somes in the wide-cross derivatives involvingcrosses of O. sativa with four wild species—O.officinalis (CC), O. australiensis (EE), O.brachyantha (FF), and O. ridleyi (HHJJ). Total ge-nomic DNA of the wild species was used as a probefor in situ hybridization with the somatic chromo-some preparations of wide-cross derivatives.

Characterization of O. sativa/O. brachyanthaderivatives. Total genomic DNA of O.brachyantha was digested with EcoRI and labeledwith biotin-14dATP. This DNA was used as a probein hybridization with the somatic chromosomepropagations of F1/BC1 and MAALs. The enzymemaceration method was used to obtain well-spreadsomatic chromosomes for in situ hybridization. Inthe F1 hybrid, all the 12 chromosomes of O.brachyantha could be identified from sativa chro-mosomes. The hybridization signal appeared darkbrown due to probe hybridization and unlabeledsativa chromosomes appeared light blue. In a simi-lar experiment, MAALs (MAAL 6 and MAAL 12)derived from O. brachyantha were used for in situhybridization. The extra chromosome of O.brachyantha showed dark brown hybridization sig-nal, making it clearly distinguishable from the re-maining 24 chromosomes of O. sativa. The tech-nique characterized introgression of alien chromo-some segments from brachyantha into the sativagenome.


Characterization of O. sativa/O. australiensisderivatives. The genomic DNA of O. australiensiswas used as a probe in in situ hybridization to char-acterize the parental chromosomes of the plant hav-ing 2n = 27 chromosomes derived from anther cul-ture of the F1 hybrid (O. sativa/O. australiensis).The probe produced uniform labeling pattern overthe entire length of all 14 O. australiensis chromo-somes (bluish-green), whereas 13 chromosomes ofsativa appeared light blue after Giemsa staining.The O. australiensis chromosomes showing the hy-bridization signal appeared bluish-green under bluelight excitation allowing the identification of all O.australiensis chromosomes, whereas the O. sativachromosomes appeared blue due to counterstainingwith 4’-6-diamidino-2-phenylindole (DAPI). Thesame cell showed green fluorescence of fluoresceinisothiocyanate (FITC) only on the 14 chromosomesof O. australiensis.

Characterization of O. sativa/O. officinalis de-rivatives. We also used fluorescent in situ hybridi-zation (FISH) to identify parental chromosomes andto locate rDNA loci in the F1 hybrid of an elitebreeding line from O. sativa/O. officinalis (acces-sion 100896). Total genomic DNA of O. officinalisand 45S rDNA used as probe were labeled by ran-dom primer labeling technique with biotin-16-dUTP and digoxigenin-11-dUTP. Posthybridizationinvolved stringent washing of the slides with 2XSSC at 42 °C and 0.1X SSC at 60 °C. FollowingFISH, and using total genomic DNA of O.officinalis as probe, parental chromosomes of O.officinalis could be distinguished in the F1 hybridfrom the sativa chromosomes. The bluish-greenFITC signal appeared on O. officinalis chromo-

somes when the hybrid cell was counterstained byDAPI. This was depicted more clearly when thesame cell was exposed to blue light and only O.officinalis chromosomes were seen as green. Hy-bridization with 45S rDNA probe showed reddishfluorescent signal of rhodamine on two chromo-somes of O. officinalis and on one chromosome ofO. sativa.

AFLP ANALYSIS OF ORYZA SPECIES

R.K. Aggarwal,35 D.S. Brar, J. Talag, S. Nandi,N. Huang, and G.S. Khush

We used AFLP markers to determine phylogeneticrelationships among Oryza species. Seventy-sevenaccessions of 23 Oryza species, five related genera,and three outgroup taxa were included in the analy-sis. AFLP data were analyzed to study species rela-tionships using different clustering algorithms, andthe resulting phenograms were tested for stabilityand robustness. AFLP analysis revealed a largenumber of distinct, scoreable fragments per primerpair. A total of 1,191 polymorphic markers wereobtained using five AFLP primer combinations (Ta-ble 5). The level of polymorphism was much lowerwithin species (~2% in O. minuta to 21% in O.officinalis) and also between species carrying simi-lar genome(or genomes) (~20% for HHJJ genometo 35% for BB/BBCC genome species). Table 5shows the distribution of AFLP markers for differ-ent genomes of Oryza, related genera, and outgrouptaxa. In general, more markers were obtained forallotetraploid Oryza species (av 46) than for theirdiploid relatives (av 33).

Table 5. Distribution of AFLP markers detected for different primer pairs, across genomes of Oryza, related genera, andoutgroup taxa. IRRI, 1998.

Primer Total Average number of markers/ Average number of markers/individual/pair poly- individual over genome in Oryzaused morphic

markers Diploid Tetraploid AA BB CC EE FF GG BBCC CCDD HHJJscored Oryza Oryza Related Outgroup

species species genera taxa

P1/M1 234 28 40 33 37 22 22 31 32 25 36 39 40 41P1/M2 260 39 52 43 49 36 37 38 37 39 45 50 51 56P1/M3 218 32 48 39 39 33 36 34 32 18 40 53 48 43P1/M4 255 39 52 47 44 37 37 36 40 40 44 52 47 57P2/M5 224 28 39 34 40 29 22 26 33 26 34 38 42 37

Av 238 33 46 39 42 31 31 33 35 30 40 46 46 47

Total 1191 166 231 196 209 157 154 165 174 148 199 232 228 234


Nei’s genetic distances (D values) showed a lin-ear increase from within species to between speciesand were most striking between different genomes.Within species, distances ranged from 0.024 (O.meyeriana) to 0.213 (O. officinalis) with the excep-tion of two accessions of O. brachyantha, whichshowed a much higher value (0.301). The averageD value between species carrying similar genome(s)was ~2.8 times (0.293) greater than within species(0.104), while between genomes of Oryza, it was0.737.

The results of AFLP analysis suggest commonancestry to the genus Oryza and indicate that

● evolution in Oryza has followed a polyphyleticpath wherein multiple lineages underwentindependent divergence after separation earlyin the evolution from a common ancestor orpool of related taxa;

● newly assigned genomes, GG for O.meyeriana and HHJJ for O. ridleyi complexes,are among the most diverged in the genus;

● CCDD tetraploids are of relatively ancientorigin among the officinalis complex;

● O. malampuzhaensis, O. indandamanica, O.alta, and O. grandiglumis are diverged enoughto deserve species status; and

● O. brachyantha is the most diverged speciesin the genus.

Rice transformation

EFFECTIVENESS OF PEPC PROMOTER IN Bt RICE

F. Alinia,36 B. Ghareyazie, L. Rubia, J. Bennett,and M. Cohen

We transformed an Iranian aromatic variety, TaromMolaii, with a construct containing a synthetic gene

for the Cry1Ab toxin from Bacillus thuringiensis(Bt) under control of the maize PEPC promoter.One advantage of the PEPC promoter is that it isactive only in green tissues and thus its use will re-sult in only limited accumulation of Bt toxin in therice grain.

The resistance of cry1Ab-transformed and con-trol plants was tested at vegetative and floweringstages with neonate and 10-d-old larvae of two stemborer species, Chilo suppressalis and Scirpophagaincertulas. Vegetative-stage cry1Ab-transformedplants were highly resistant to neonate larvae ofboth species but the cry1Ab-transformed and con-trol plants did not differ in resistance to 10-d-oldlarvae (Table 6). At flowering stage, the survival ofneonate S. incertulas larvae, but not 10-d-old larvae,was significantly lower on the cry1Ab plants thanon control plants. Survival of C. suppressalis larvaeof both age classes did not differ significantly oncry1Ab-transformed and control plants. Our resultssuggest that Bt toxin genes under control of thePEPC promoter alone will not provide satisfactorycontrol of rice stem borers.

TRANSGENIC APPROACHES TO TUNGRO VIRUS

O. Azzam, E.L. Coloquio, Z. Flores, A. Klöti,37

J. Fütterer,37 and I. Potrykus

Tungro is a complex disease associated with ricetungro spherical virus (RTSV) and rice tungrobacilliform virus (RTBV). A green leafhopper(Nephotettix virescens) transmits and spreadstungro throughout South and Southeast Asia.IRRI’s strategy to breed for a durable resistance totungro has encompassed incorporating vector andvirus resistance genes by conventional breeding ap-proaches. Because no natural resistance to RTBV

Table 6. Percent larval survival of two stem borer species at 7 d after infestation on cry1Ab-transformed and controlplants. IRRI, 1998.

Vegetative stage Flowering stageSpecies Larval age

cry1Aba Control Difference cry1Aba Control Difference

C. suppressalis Neonate 1.25 + 1.25 61.25 + 13.44 60.00 ** 18.75 + 10.87 13.75 + 4.30 5.0010-d-old 62.50 + 11.09 75.00 + 9.57 12.25 82.50 + 4.79 77.50 + 4.79 5.00Difference 61.25 ** 13.75 63.75 ** 63.75 **

S. incertulas Neonate 1.25 + 1.25 25.00 + 5.40 23.75 ** 17.50 + 1.44 5.00 + 2.04 12.50 *10-d-old 22.50 + 7.50 35.00 + 5.00 12.50 47.50 + 7.50 40.00 + 8.16 7.50Difference 21.25 ** 10.00 30.00 * 35.00 **

a Mean ± SE of percentage live larvae of 20 larvae plant-1. n = 4 plants.


has yet been transferred to commercial rice varie-ties, work was initiated to induce RTBV resistancein rice using several antiviral transgenic strategies.

The strategies included expression of RTBVopen reading frame 1 (ORF1), putative viral coatprotein, viral replicase, mutated fragments of thereplicase, and production of different parts (senseand antisense) of ORF4. We used particle bombard-ment of the rice scutella and rice suspension cells toproduce fertile trangenic TP309 and Kinuhikariplants (japonica rice varieties). Two sources of vi-rus inocula were used to evaluate R1 progeny resist-ance to RTBV and RTSV. Nineteen transgenic lineswith complete copies and 32 lines with rearrangedcopies of the transgenes were evaluated.

Using either the greenhouse or Famy virus popu-lations, none of the lines tested showed resistanceto RTBV or RTSV. Almost all the inoculated plantsexhibited severe symptoms (stunted growth and leafdiscoloration) 20 d post-inoculation (dpi) and viralcoat protein titers, as measured by the enzyme-linked immunosorbent assay (ELISA), were compa-rable with those from the nontransgenic controlplants. Titers varied among individual plants fromdifferent lines. Some had high-RTSV and -RTBV5titers while others had low-RTSV but high-RTBVtiters. Based on the ELISA results and visual scores,none of the tested lines recovered at 40 dpi. Theaverage symptom severity was about 7 per line, in-dicating that most plants exhibited stunted growthand leaf discoloration.

The 32 remaining lines, which mostly hadantisense RNA constructs of ORF4, were testedusing only the greenhouse virus population and re-sults were similar to those obtained earlier. None ofthe lines showed resistance to RTBV 20 dpi andplants did not recover after 40 dpi.

Although no RTBV-resistant lines were found,several new antiviral strategies were identified.These will enhance the low expression of transgenethat was observed throughout these experiments andshould induce a resistance response.

Organization of the International MolecularBreeding Program (IMBP)

Rice breeding programs or biotechnology laborato-ries, or both, of 30 institutions from 14 Asian coun-tries plus Egypt in Africa have shown interest inparticipating in IMBP. Fifty-four scientists (12 ge-

Exploiting biodiversity for sustainable pestmanagement

Rice pests reduce yields and yield stability. How-ever, some pest management practices, such aschemical insecticides, are harmful to the environ-ment. Other practices, such as host plant resistancebased on single genes, may contribute to additionalyield instability. The effectiveness of rice pest man-agement can be improved by increasing bio-diver-sity. Research in this project extends from molecu-lar genetics to landscape ecology.

DNA sequence variation in rice tungrovirusesO. Azzam, P.Q. Cabauatan, M. Arboleda,I. Uyeda,19 M. Isogai,19 T. Omura,20 H. Hibino,20

H. Koganezawa,21 and U. Melcher22

Several biological variants of RTSV and RTBVhave been identified at IRRI since 1993 and charac-terized based on their reaction to differential hosts.

RESISTANCE-BREAKING MECHANISM IN RTSV-Vt6-

TKM6

The maintained variant for RSTV, RTSV-A, differsfrom RTSV-Vt6 in virulence on TKM6 rice variety.To understand the resistance-breaking mechanismin the RTSV-Vt6-TKM6 system, and to identifygenes that can confer a more broad and durable re-sistance to the virus, RTSV-Vt6 was characterized

neticists and 42 breeders) were nominated by theparticipating institutions to coordinate and executethe proposed activities.

A total of 177 diverse rice lines were recom-mended as the materials for the breeding efforts. Ofthose, 75 elite rice lines are currently grown onmore than 60% of the rice lands in Asia and will beused as the core gene pool lines. The rest of the ac-cessions, possessing unique alleles for specific tar-get traits, will be used as donor gene pool lines forintrogression and identification of desirable QTLs.These lines (except those from India) were plantedin an IRRI screenhouse for seed increase. Seed willbe sent to all participating NARS in May 1999.

Matching funds were provided by China andThailand to support the research activities in thefirst phase of the project.


molecularly. Extracted viral RNA was amplified byreverse transcriptase polymerase chain reaction(RT-PCR). The PCR products were then cloned andthe complete nucleotide sequence was determinedfrom multiple clones that covered the whole ge-nome. The full-length sequence of 12,171nucleotides was compared with the published se-quence of RTSV-A. The overall identity betweenthe two strains was respectively 90% and 95% at thenucleotide and amino acid levels. The many se-quence differences were scattered over the entiregenome and no potential hypervirulent region wasidentified. A full-length infectious cDNA of RTSV-A or RTSV-Vt6 will be needed to identify proteinsinvolved in the virulence of strain RTSV-Vt6.

DIFFERENTIAL REACTIONS OF RTBV VARIANTS

Three biological variants for RTBV, G1, G2, and Ic,which originated from the same IRRI greenhousevirus isolate, were cloned and sequenced. Thesevariants showed differential reactions on rice varie-ties FK135 and TN1. The genome sizes of the threevariants differed but were respectively 95% and99% identical at the nucleotide and amino acid lev-els. The analysis of restriction endonuclease mapsfor the RTBV genomes identified EcoRV, PstI, andEcoRI as potential enzyme markers to differentiatebetween the Ic-G1 pair and the other isolates.

Alignment of these sequences with publishedRTBV sequences (Phi-1, Phi-2, and Phi-3), whichoriginated from the same IRRI greenhouse isolate,and with a recently published Malaysian sequence(Serdang), showed that the cysteine-rich region ofORF3 is the most variable region (Fig. 5). This re-gion contains a cysteine-histidine motif that is con-served among retroelements and is thought to bindRNA during packaging of the pregenomic RNA toseparate it from cellular RNAs as the template forreverse transcription. The observed changes inamino acid sequences were conserved in the G1, Ic,and Serdang isolates as compared with the other iso-lates. This suggests that the cysteine-rich regionmay affect the virus infection cycle and the pheno-typic differences among the variants.

IR64 deletion mutants for functionalgenomicsH. Leung, C. Wu, M. Baraoidan, and G. Khush

Rice, with the smallest genome of all cereals, is thefocus of an international sequencing effort and islikely to be completely sequenced within a decade.The DNA sequences represent an enormous pool ofmarkers and genes for rice improvement throughMAS or transformation. A full exploitation of thiswealth of information will not be possible, however,until the biological functions encoded by thesequenced DNA are understood.

We began a systematic production of mutantswith the goal of assigning available sequencedDNA to biological functions revealed by the muta-tions. Focus is on the production of deletion lines,which will allow physical detection of mutations inthe genome using available expressed sequence tags(ESTs) and other cloned DNA sequences. We rea-son that the nontransgenic deletion mutants willmeet needs not met by transgenic insertion mutants

5. Comparison of the predicted amino acid residues no. 842-948in the cysteine-rich region of the seven RTBV isolates. Phi-1(EMBL Acc. no. X57924), Phi-2 (EMBL Acc. no. M65026),Phi-3 (EMBL Acc. no. D10774), Serdang (EMBL Acc. no076470). Amino acid substitutions are underlined and in boldletters. IRRI, 1998.


and will accelerate trait discovery in rice throughthe use of advancing genomic technologies (Fig. 6).

We concentrate on the production of mutants inIR64, which carries many valuable agronomic traitsand tolerance for biotic and abiotic stresses. Thus,creating mutations in IR64 can facilitate detectionof phenotypic changes in important agronomictraits.

Diepoxybutane (DEB, 0.004-0.006%) and fastneutrons (FN, 33 Gy) were used to generate morethan 30,000 M3 lines with potential deletions and

chromosomal rearrangements. A gamma ray (GR,250 Gy)-treated population was also produced tocompare the spectrum and molecular characteristicsof the mutations produced by different mutagenictreatments. Chlorotic or albino mutants were ob-served respectively in 8 and 10% of M2 lines in theDEB and GR populations. More than 3,200 M2 lineswere screened with four diverse blast fungus iso-lates and susceptible plants were detected in 0.4%of the M2 populations. Disease-lesion-mimic mu-tants were detected at 0.1% in the DEB population.

6. Deletion mutant bank in the framework of functional genomics. Initial focus is on using candidate genes in the disease defensepathways to characterize the mutants.

Discover new traits

Rice mutant bank

DNA sequences fromrice and other cereals

Screen for agronomic traits:gain or loss of functions

Identify new genesEvaluate allelic diversity and functions

Improved rice productivity with NARS partners:breeding, marker-aided selection, transformation

Assign DNA tomutant phenotypes

GAGGATTCGGGATTAGGGCTTAGTATGGCTTTAGGGCTTAGGGCTTAGAAATTCCATATAAGATCTTCCTTCCAACAACCGCTCAGAGAAGAACCAAGTCCTCTCTCTTAATTTAAGGAGAGGAATTTCCTCCG

GAGGATTCGGGATTAGGGCTTAGTATGGCTTTAGGGCTTAGGGCTTAGAAATTCCATATAAGATCTTCCTTCCAACAACCGCTCAGAGAAGAACCAAGTCCTCTCTCTTAATTTAAGGAGAGGAATTTCCTCCG


The phenotypes observed in M2 indicate a richsource of mutations present in the IR64 collection.These mutant lines are being mass increased in theM3 generation for screening of a variety of traits. Todevelop a system for reverse genetics, candidatedisease defense genes are being used to survey apanel of DNA from individual deletion lines se-lected for altered response to BB and blast.

The empirical mutation rate (about 0.1%) ob-served in rice mutants induced by chemicals or ion-izing irradiation suggests that each mutant probablyharbors 10-20 mutated sites. The goal is to produce40,000 independent deletion lines to give a 95%chance of detecting a mutation in most genes (ex-cept homozygous lethals). We expect to advance allthe DEB mutant lines to M3 (about 19,000 lines) byearly 1999. Additional disease-susceptible and dis-ease-resistant mutants will be identified through theongoing screening for gain and loss of disease re-sistance.

Bacteria with disease antagonism and plantgrowth-promoting propertiesZ. Chen, R. Pamplona, E. Regalado, B. Cottyn,and T.W. Mew

Bacteria were isolated from seeds and blast lesionscollected from farmers’ fields in Iloilo and Rizalprovinces, Philippines, and plated on various media.Morphologically distinct bacterial colonies wereselected and studied for cell morphology, patho-genicity, antagonism to the pathogens Rhizoctoniasolani and Fusarium moniliforme, plant growth-promoting ability, and genetic diversity. The 63Bacillus spp. isolates from blast lesions showed ahigher proportion of antagonism and stronger an-tagonism than the 32 Gram negative isolates fromthe seed washes. None of the isolates from blast le-sions had plant growth-promoting properties. Eightisolates from the seed washes promoted seedlinggrowth and four isolates promoted taproot growth.Some isolates from the seed washes reduced seed-ling growth. Five of the eight growth-promotingisolates from the seed washes also showed antago-nism to pathogens, indicating that some Gram nega-tive bacteria on seeds have multiple beneficial ac-tivities.

Forty-one bacterial isolates, 18 positive and 23negative for antagonism by the dual culture test,were selected for generating DNA markers diagnos-

tic for antagonistic isolates of Bacillus amylo-liquefaciens. Based on their RAPD fingerprints,those isolates were found to cluster at 65-99% simi-larity with 8 isolates that were previously identifiedas B. amyloliquefaciens by the fatty acid methyl es-ter (FAME) method.

In a preliminary test, 124 RAPD primers werescreened for their ability to differentiate four iso-lates that included 2 antagonistic and 2 nonantago-nistic B. amyloliquefaciens. Four primers (AM-18,AM-04, AA-01, AA-09) amplified fragments thatwere specific to the antagonistic isolates. Furthertesting with 37 isolates (16 antagonistic and 21 non-antagonistic) showed that AM-18 was the most ef-fective in differentiating the isolates. AM-18 ampli-fied an approximately 1,100 bp band with all an-tagonistic isolates except G327, G458, and G460,and was absent from the nonantagonistic isolates(Fig.7). These results indicate the usefulness ofRAPD primers in identifying antagonistic strains ofB. amyloliquefaciens.

Heritability of Bt tolerance in the stripedstem borerF. Alinia, F. Gould,23 and M.B. Cohen

It is important to anticipate the development of re-sistance to new insecticides and useful to estimatethe rate at which insect resistance can develop.Many groups are working to produce rice trans-formed with insecticidal toxin genes from Bacillusthuringiensis (Bt) for improved protection againststem borers. It has already been demonstrated thatinsect pests of several crops can evolve resistanceto Bt toxins. We examined the heritability of toler-ance for a Bt toxin in a population of the stripedstem borer, Chilo suppressalis (Lepidoptera:Pyralidae).

We estimated the narrow-sense heritability oftolerance for a Bt toxin, Cry1Ab, with a half-sib de-sign in which each of 20 striped stem borer maleswas mated to two females. Two-thirds of the prog-eny of each cross were tested for survival on an ar-tificial diet containing 0.03% Cry1Ab toxin byweight, and one-third for survival on a control diet.Mortality was scored 5 d after diet infestation. Her-itability was calculated using standard formulaswith the assumption that mortality was a thresholdcharacter with tolerance for Cry1Ab as the underly-ing continuous variable.


Table 7. Mortality data used in calculation of heritability of Cry1Ab tolerance in a striped stem borer population. IRRI,1998.

Mortality (%) Mortality (%)Male Female Male Female

Cry1Ab Control Cry1Ab Controldiet diet diet diet

1 1 90 0 11 1 40.0 02 89.6 3.3 2 35.0 0Mean 89.8 1.7 Mean 37.5 0

2 1 79.2 3.3 12 1 50.0 6.72 85.0 0 2 23.3 0Mean 82.1 1.7 Mean 36.7 3.3

3 1 73.3 0 13 1 25.6 02 55.8 0 2 46.7 0Mean 64.6 0 Mean 36.1 0

4 1 40.0 6.7 14 1 33.3 02 86.7 6.7 2 38.3 0Mean 63.3 6.7 Mean 35.8 0

5 1 43.3 0 15 1 18.0 13.32 81.7 0 2 50.0 26.7Mean 62.5 0 Mean 34.0 20

6 1 75.0 0 16 1 50.0 6.72 43.3 0 2 15.0 3.3Mean 59.2 0 Mean 32.5 5

7 1 58.3 0 17 1 31.7 3.32 56.7 0 2 25.0 0Mean 57.5 0 Mean 28.3 1.7

8 1 60.0 0 18 1 36.7 02 45.0 0 2 18.3 0Mean 52.5 0 Mean 27.5 0

9 1 26.7 0 19 1 28.3 02 71.7 0 2 18.3 0Mean 49.2 0 Mean 20.8 0

10 1 31.7 0 20 1 8.3 02 63.3 0 2 16.7 6.7Mean 47.5 0 Mean 12.5 3.3

7. RAPD analysis of DNA from antagonistic (+) and nonantagonistic (-) Bacillus amyloliquefaciens isolates with primer AM-18.IRRI, 1998.

3054 bp

2036 bp

1636 bp

1018 bp

1 k

b m

arke

r

B.

subt

ilis

9-1

66

9 +

59

+3

27

+4

12

+4

26

+4

60

+4

58

+4

55

+3

46

+4

37

+4

17

+8

3+

82

+8

1+

61

+4

5+

22

9+

39

6+

46

2-

33

5-

26

7-

44

4-

34

5-

34

4-

44

7-

84

-7

8 -

38

-3

65

-3

66

-4

59

-4

02

-4

16

-3

64

-3

52

-4

25

-4

41

-4

43

-4

52

-4

34

-4

33

-


Mean family mortality on the Cry1Ab-treateddiet ranged from 89.8 to 12.5% (Table 7), and theeffect of male parent on larval mortality was highlysignificant. There was no correlation between mor-tality on Cry1Ab and control diet (r=-0.02, P=0.90,n=20 males), suggesting that differential mortalityof the families on Cry1Ab diet was due to their dif-ferential sensitivity to the toxin used. The narrow-sense heritability for the test population was 0.52,meaning that 52% of the variation in mortality onthe Cry1Ab diet was attributable to genetic differ-ences. This is a relatively high value in comparisonwith those from other studies of insect heritabilityto insecticides, and indicates the importance of care-fully designed resistance management strategies todelay the evolution of Bt resistance in striped stemborer populations.

Invertebrate biodiversity in a Philippinefarmer’s fieldK.G. Schoenly, H.D. Justo, Jr.,2 A.T. Barrion,M.K. Harris,24 and D.G. Bottrell25

Most invertebrate biodiversity studies in tropicalrice systems have focused on the fauna of the plantcanopy. Rarely have the canopy and the floodwaterbeen studied collectively. This study compared tem-poral trends in community structure of invertebratesinhabiting the terrestrial (plant canopy) and aquatic(floodwater) portions of the rice ecosystem.

Rank abundance curves and indices of commu-nity structure were applied to invertebrate time-se-ries data collected from a farmer’s irrigated ricefield in Calauan, Laguna Province, Philippines.Canopy and floodwater invertebrates were vacuum-and strainer-sampled at roughly weekly intervalsfrom seedling to harvest for a total of 8 samplingdates. The cumulative samples included 202 taxaand 9,570 individuals for the plant canopy and 180taxa and 84,905 individuals for the floodwater.

Rank abundance curves (Fig. 8) revealed● a 10,000-fold range in invertebrate abundance

with many abundant taxa remaining abundantover all crop stages;

● lower evenness (equitability) of invertebrateabundances in the floodwater than the plantcanopy, due in large part to the numericaldominance (75%) of two crustaceans [Hetero-cypris luzonensis Neale, and Eucyclopsserrulatus (Fischer)];

● the preponderance of natural enemies as thelargest guild in number of taxa in both thecanopy and floodwater, followed by herbi-vores, detritivores, and tourists (nonpredatorytaxa with no known interaction except as preyto ricefield predators); and

● herbivore- and detritivore-dominated faunasrespectively typified early crop periods in thecanopy and floodwater, followed by predator-dominated faunas in both systems at mid- andlate-crop stages. Rates of community turnovergenerally increased with crop age in both thecanopy and floodwater faunas, with the formerincreasing faster than the latter.

Effect of water management on sheath blightspreadS. Savary, L. Willocquet, N. Castilla, D. Flura,26

and L. Huber26

Water for agricultural use is becoming scarceworldwide, and growing rice with less water is amajor challenge. A 1998 DS study at IRRI exam-ined how water-saving measures in growing riceaffect sheath blight epidemics. The spread of sheathblight in transplanted rice with two levels of watermanagement (continuously flooded and flashflooded) was compared. The water level in the con-tinuously flooded crop was maintained at about 5cm above the soil surface. In the flash-flooded crop,water was introduced to the field regularly to main-tain a saturated soil. Artificial disease sources wereestablished (i.e., rice hills were inoculated withsheath blight) at weekly intervals in each watermanagement level. Inoculations were done at 34,41, and 48 d after transplanting in three differentsites in each water treatment. The disease foci thatdeveloped were monitored at weekly intervals.Sheath blight severity on the leaves of the eight hillsadjacent to an inoculated hill was assessed weeklyfrom 1 to 3 wk after inoculation.

Sheath blight severity was higher (Table 8) in theflash-flooded crop, i.e., when water saving was at-tempted. The effect of water management was sig-nificant (P<0.05) at each observation date, for allthree generations. The effect of water managementon sheath blight was attributed to the differences inamount of free water present on the canopies.

Free water on the canopy was monitored using afour-point leaf wetness rating scale on three layers


8. Ranked-abundances and functional-group composition of canopy (A) and floodwater (B) invertebrates for each of eight crop stages.Numbers above each curve give the sampling date (d after transplanting, DT), number of taxa, and number of individuals. For clarity ofpresentation, curves were truncated at 10 individuals per taxon. Counts of canopy and floodwater taxa are numbers per 60 (initial) ricehills per sampling date. IRRI, 1998.

10,000.000

1,000.000

100.000

10.000

1.000

0.100

0.010

0.001

0.000

100,000.000

10,000.000

1000.000

100.000

10.000

1.000

0.100

0.010

0.001

0.000

D (9%) >H(30%) >E (59%) >T (2%) >

D (11%) >H(26%) >E (62%) >T (1%) >

2 12 24

75% 90% 95%

0 20 20040 60 80 100 120 140 160 180

0 20 20040 60 80 100 120 140 160 180

Rank order of invertebrate abundance

150 180

23

75%58

90% 95%165 202

A. Canopy

B. Floodwater

Mean and range of invertebrate abundances

82

Table 8. Sheath blight severity at two levels of water managementa and three generations of foci. IRRI, 1998 DS.

Generation 1b Generation 2 Generation 3Observationa (wk) Mean

FF CF FF CF FF CF

1 0.221 0.029 0.325 0.091 0.756 0.175 0.434 0.3702 0.224 0.043 0.488 0.133 1.134 0.138 0.615 0.1053 0.578 0.077 0.875 0.259 1.152 0.087 0.868 0.141

aObservations were made at weekly intervals from 1 to 3 wk after inoculation of source hill. bFF = flash-flooded, CF = continuously flooded.


9. Estimated weight of free water at 0630 h over time in a flash-flooded and a continuously flooded rice crop. a) upper layer; b) middlelayer; c) lower layer of the canopy. Horizontal bars indicate the monitoring of three generations of sheath blight foci. IRRI,1998 DS.

5

4

3

2

1

0

5

4

3

2

1

0

5

4

3

2

1

0

Generation 1Generation 2

Generation 3

c

b

a

Flash floodedContinuouslyflooded


Generation 3


Generation 3

98 105 112 119 126 133

Julian days

Weight of free water (mg cm-2)


Assessing opportunities for N2 fixationin rice

The project goal is to make rice amenable to symbi-otic N2 fixation. In collaboration with scientists atthe National Institute for Agrobiological Resources,Japan, and the French Institute of Agronomical Re-search/National Center for Scientific Research(INRA/CNRS), this activity examined

● the occurrence and expression of thehomologues of legume early nodulin (ENOD)genes in rice, and

● the ability of rice to perceive rhizobial Nodfactors.

Homologues of legume ENOD genes in riceP.R. Reddy, J.K. Ladha, D.S. Brar, andH. Kouchi27

Investigations of legume symbioses have identifiedcritical genetic components that are important forthe accomplishment of symbiosis, but the presenceof those components has not been assessed in rice.We initiated investigations on identification andcharacterization of homologues of ENOD genes inrice to determine the genetic predisposition of ricetoward rhizobial infection.

Eighty rice accessions from 23 Oryza specieswere examined for the presence of the homologuesof ENOD genes. Southern blot analysis of genomicDNA was performed on nylon membranes using

32P-labeled cDNAs of legume ENOD genes asprobes to visualize the homologues of ENOD genesin rice.

The membranes were subsequently autoradio-graphed, and differences in the hybridization signalobtained were measured semi-quantitatively byscanning densitometry. For the estimation of hy-bridization differentials, the values obtained with aparticular ENOD probe were normalized relative tothe total hybridization signal intensity of the bandsderived from the soybean genomic DNA probedwith the same ENOD cDNA.

Southern analyses revealed a widespread distri-bution of homologues of ENOD genes across allgenomes of rice. The degree of cross-hybridizationof the legume ENOD genes with sequences in thegenomes of various species, however, suggests thatthe homologues of ENOD genes are conserved tovarious extents in different Oryza species and re-lated genera. Hybridization differentials derivedfrom semi-quantitation of the hybridization signalsindicated that the homologues of ENOD2 are rela-tively better conserved in O. sativa, O. rufipogon,O. longistaminata, O. nivara, and O. perennis.ENOD5 is better conserved in O. punctata, Oeichingeri, O. minuta, and O. malampuzhaensis;ENOD12 in O. australiensis and O. brachyantha;ENOD14, ENOD40, and ENOD55 in O.brachyantha; ENOD70 in O. australiensis, andENOD93 in O. sativa, O. rufipogon, O. nivara, O.rhizomatis, O eichingeri, O. minuta, O. latifolia,and O. malampuzhaensis (Fig. 10). The fact thatENOD gene homologues exist widely in dicots andmonocots is evidence that these homologues havearisen from a common ancestral plant. The ENODgenes in legume plants apparently acquired nodule-specific symbiotic functions as a result of gene du-plication after the divergence of dicots andmonocots.

Characterization of the homologues oflegume ENOD93 from riceP.M. Reddy, J.K. Ladha, and H. Kouchi27

The presence of homologues of ENOD genes in awide variety of rice species denote that the biologi-cal functions of early nodulins may be diverse andnot restricted to nodule organogenesis alone. Hence,we set out to characterize the rice homologues toascertain how closely they are related to their leg-

of the canopy throughout the experiment. The ratingscale was 0 = dry, 1 = with a few scattered big drop-lets, 2 = a thin film of small droplets, and 3 = a densefilm of small droplets. Visual observations weremade daily at 0630h. Leaf wetness at that time of theday was considered to represent the amount of dewand guttation water formed on the canopy.

The rating scale was translated in waterweights and the weight of free water on all layers ofthe canopy was higher in the flash-flooded than inthe continuously flooded crop (Fig. 9), particularlytrue in the beginning of the experiment. Differencesin leaf wetness were stronger in the upper and mid-dle layers of the canopy.

This experiment suggested that attempts to savewater could favor a disease such as sheath blight. Asimilar reasoning could apply to other diseases, suchas blast or bacterial leaf blight.


10. Southern blots of DraI-digested DNA of Oryza species that gave strong hybridization signals with 32P-labeled legume ENODcDNA probes. O. sativa (Os – genome AA; Accessions IR31917, IR56, IR64); O. rufipogon (Or – AA; 105908, 105909, 105910,106412, 106423); O. longistaminata (Ol – AA; 103886, 103890, 103902); O. barthii (Obr – AA; 101937); O. nivara (On – AA;103407, 105721, 106185); O. perennis (Opr – AA; 104823); O. punctata (Op

2 – BB; 103896, 104064, 105690, 105980); O. punctata

(Op4 – BBCC; 100884, 101409, 104975); O. eichingeri (Oe – CC; 101424, 105181, 105182, 105408, 105413); O. malampuzhaensis

(Om – BBCC?; 105223, 105328); O. brachyantha (Ob – FF; 101232, 94-10482). IRRI, 1998.

ume counterparts. We initially characterized thehomologues of infection-related legume ENOD93gene in rice (O. sativa).

A rice (O. sativa var. Nipponbare) cDNA libraryderived from poly(A)+ RNA of suspension-culturedcells, as well as its genomic library, were screened.We used digoxigenin-labeled rice-expressed se-

quence tags (ESTs) that showed similarity tosoybean ENOD93, as probes to isolate cDNA andgenomic clones of the homologues of GmENOD93from rice.

The library screening was done on nylon mem-brane replicas. Positive clones were plaque-puri-fied, phage DNA was isolated, and cDNA and ge-

OsENOD93aGmENOD93OsENOD93b



* * * ** ***** * ** *** ** ***

MATVTRAHLEQRLALAKRCSREANIAGVKAAAVATIASA

MAKGNSPLERPSLASLDQKLAFAKRCSHEGVLAGAKAAVVASVASA

MAARSFQARSPKEESDAAVHEAVTLGLKNAAISGTVVA

** * * * * *

************ ** * * ***** ** *** *** * *

VPTLASVRMLPWAKANINPTGQALLIICTAAGMAYFVAADKKILSLA

IPTLASVRMLPWARANLNHTAQALIISTATAAAYFIVVADKTVLATA

VPTLVGCRVLPWAKANLNYTAQALIISAACIAGFFITADKAILRNA

*** * **** **** ******* * * ** *** * *

* **

RRHSFENAPPEHLKNTSFQGTGRPHPAFFRP

RKNSFNQPSNSEA

RQNTIGKIDRST

* * *

39

46

38

85

92

84

115

105

96

Os Os Os Or Or Or Or Or O1 O1 O1 Ob1 On On On Op1 Op2 Op2 Op2Op2 Op4Op4 Op4 Oe Oe Oe Oe Oe Om Om Ob Ob Ob Ob Ob Ob

ENOD

2

ENOD

5

ENOD

14

ENOD

40

ENOD

55

λ (Kb)

23.1

9.4

6.6

4.4

2.32.0

0.6

11. Comparison of deduced amino acid sequences of OsENOD93a and OsENOD93b of O. sativa showing homology to GmENOD93.Asterisks denote the amino acids in OsENOD93a and OsENOD93b that are identical to GmENOD93. IRRI, 1998.


nomic inserts were subcloned into pBluescript IISK+ and sequenced by the dideoxy-chain termina-tion method. The DNA sequences were comparedwith sequences deposited in the GenBank databaseusing the BLAST program, and additional compu-ter analyses were performed using the GCG pack-age. For northern analysis, total RNA was electro-phoresed, blotted onto nylon membranes, and hy-bridized with 32P-labeled cDNA probes.

The investigations revealed that rice possessestwo different homologues of the GmENOD93.Analysis of the cDNA clones of rice homologuesshowed that OsENOD93a has an ORF with a cod-ing sequence homology of 58.2% to GmENOD93,whereas the ORF of OsENOD93b has displayed ahomology of 42.3% (Fig. 11).

Total RNAs from various tissues of rice weresubjected to RNA transfer blot analysis to examinethe organ-specific expression of OsENOD93a andOsENOD93b. Those exhibited different organ-specific expression patterns (Fig. 12). In intact ricetissues, OsENOD93b was most abundantly ex-pressed in roots and at much lower levels in etio-lated and green leaves, whereas the expression ofOsENOD93a was low in roots and etiolated leaves,and not detected in green leaves. Predominant ex-pression of the rice homologues in rice roots indi-

cates that they have a special function in roots. It isyet to be determined, however, whether their ex-pression increases, similar to that in soybean, whenrice root tissues are infected by bacteria.

OsENOD93a expression was extremely high insuspension-cultured cells, whereas that ofOsENOD93b was similar to the level found in roots(Fig. 12). Abundant expression of OsENOD93a insuspension-cultured cells suggests that the induc-tion of OsENOD93a has a crucial function in undif-ferentiated rice tissues.

Because chitin oligomers are structurally similarto rhizobial Nod factors and can induce expressionof early nodulin genes such as ENOD40 in Glycinesoja roots, it was important to determine whetherthe application of chitin oligomers to suspension-cultured cells could alter the expression ofOsENOD93a or OsENOD93b.

Northern analysis demonstrated that, similar tothat of legume ENOD93, the expression of bothOsENOD93a and OsENOD93b was not enhancedby the application of chitin oligomer (heptamer, 1µg ml-1; Fig. 12).

Ability of rice to perceive rhizobial nodfactorsP.M. Reddy, J.K. Ladha, S.K. Datta, K. Datta,M.C. Ramos, F. Maillet, R.J. Hernandez,L.B. Torrizo, and N.P. Oliva

Proteins encoded by the activated nod genes ofrhizobia aid the synthesis of extracellularlipochitooligosaccharide signal molecules, knownas Nod factors, which play a pivotal role in deter-mining the fate of the symbiotic interaction. Puri-fied Nod factors were shown to elicit a number ofresponses on the roots of legumes, such as deforma-tion of root hairs, cortical cell divisions, and the for-mation of nodule primordia, as well as nodules. Inaddition, Nod factors mediate transcriptional activa-tion of early nodulin genes, such as ENOD2,ENOD5, ENOD12, ENOD40, and rip1, the prod-ucts of which are involved in the early steps of thenodulation processes. These findings demonstratethat Nod factors play a crucial role in initiating theprocesses leading to N2-fixing nodule developmentin legumes. Determining whether rice can respondto Nod factors could lead to strategies that wouldmake rice amenable to develop a N2-fixingendosymbiotic association with rhizobia. Hence, we

12. Expression of OsENOD93a and OsENOD93b homologuesin O. sativa roots, etiolated and green leaves, and calli treatedwith heptameric chitin oligomer (upper panel). rRNA bandsstained with methylene blue were used as standards to confirmthat about equal amounts of total RNA were added to each lane(lower panel). The numerals within parentheses indicate thelength of the transcripts in kilobases. Lane 1, roots; lane 2,etiolated leaves; lane 3, green leaves; lane 4, suspension culture;lanes 5-7, suspension culture treated with chitin oligomerheptamer, 1 µg ml-1) for 15, 60, and 120 min, respectively. IRRI,1998.

1 2 3 4 5 6 7

OsEN93Ha (0.8 Kb)

OsEN93Hb (0.6 Kb)

25S rRNA


initially tried to determine whether Nod factors arerecognized by rice.

MtENOD12 gene expression was shown to be anexcellent molecular marker for Nod factor percep-tion in alfalfa. To ascertain whether Nod factors areperceived by rice, we used the MtENOD12 pro-moter fused to the gusA (uidA) reporter gene andgenerated transgenic plants of three rice varieties(Taipei 309, Chinsurah Boro II, and IR58) carryingthe MtENOD12-GUS fusion gene.

Transgenic rice plants were first incubated infresh Fahraeus medium, supplemented with or with-out ammonium nitrate (10 mM) for a period of 4-6d prior to subjecting the roots to 6-24-h or 48-htreatment with a mixture of sulfated and nonsulfatedNodNGR factors. NodNGR factors (10-6-10-9 M)were added directly to the medium containing eithertransgenic plants in tubes or excised root segmentsderived from the transgenic plants. Roots werestained for histochemical localization of GUS atvarious times during NodNGR factor incubation.

No GUS expression was normally observed un-der N2-limiting conditions in the roots when nottreated with NodNGR factors. On rare occasions,roots displayed faint GUS activity, which wasstrictly confined to parenchyma tissue surroundingvascular elements in stele. However, as much as80% of the roots of the transgenic plants grown inN2-limiting conditions, upon treatment withNodNGR factors, showed conspicuous GUS ex-pression. It was specifically in cortical parenchymain the elongation zone behind the root tip and at thesites of lateral root emergence (Table 9, Fig. 13 a-e,

13. Histochemical localization of GUS activity in calli and rootsof transgenic rice carrying the MtENOD12-GUS in response toNodNGR factors. Nod factor-elicited expression of GUS in theroots of transgenic (a)-(f) Taipei 309, (i)-(n) Chinsurah Boro IIand (o)-(s) IR58, and (g)-(h) transgenic calli of Taipei 309. IRRI,1998.

Table 9. Expression of the MtENOD12-GUS in roots of Taipei 309 in response to different concentrations of NodNGRfactors. Root systems of three transgenic plants were analyzed. Excised roots were incubated for 24 h in the N2-freemedium containing different concentrations of elicitors prior to visualizing GUS expression. IRRI, 1998.

Concentration (M)a

Elicitor0 10-9 10-8 10-7 10-6

NodNGR factors 0/15 (0 %) 9/18 (50 %) 8/15(53 %) 12/17 (71 %) 15/18(83 %)[++] [++] [+++] [++++]

NodNGR factors 0/19 (0 %) 7/17 (41 %) nd nd 13/17 (77 %) (sulphated) [+] [+++]NodNGR factors 0/23(0 %) 12/26 (46 %) nd nd 11/15 (73 %) (nonsulphated) [+] [+++]N, N’,N’’,N’’’- 0/15 (0 %) 0/21 (0 %) 0/16 (0 %) 0/14 (0 %) 0/20 (0 %)tetraacetylchitotetraose

a Values depict number and percentage of roots expressing MtENOD12-GUS fusion in cortical parenchyma in response to the treatment withelicitors. Intensity of GUS expression: (+) low; (++) medium; (+++) high; (++++) very high. nd: not determined.

i-k, and o-s). In contrast, roots of transgenic ricegrown in the presence of combined N, whether ornot supplemented with NodNGR factors, showed

b

c d e f

Ex EpEn

Pc

CsYp

a

g

h

i j k

l m n

Ep

Ex Cs

EpEx

C1

q r S

En

Pc

Yp

o

p


no GUS activity at all. Taken together, these find-ings clearly demonstrated that the rice roots per-ceive NodNGR factors, and these rhizobial signalmolecules are able to efficiently mediate the activa-tion of MtENOD12-GUS fusion in the rice rootsonly when the plants were starved of N.

Our study showed that the MtENOD12 promoteris activated in rice by rhizobial Nod factors. Thefindings imply that rice has a mechanism to per-ceive Nod factors and also possesses a signal trans-duction system to enable subsequent activation ofthe legume early nodulin promoter. As in legumes,the presence of excess combined N in the growthmedium inhibited the expression of the symbiosis-related gene MtENOD12 in rice in response to Nodfactors. This implies that Nod factor action onMtENOD12 expression in rice is controlled by theN-status of the plant, suggesting that at least a partof the N2-mediated regulatory mechanism(ormechanisms) responsible for symbiotic responses inlegumes is conserved in rice.

Previous work found that NodNGR factors wereunable to induce root hair deformation in rice (IRRIprogram report for 1996). In the current study, Nodfactors failed to elicit MtENOD12-GUS expressionin epidermal cells including root hairs. The appar-ent inability of epidermal cells to respond to Nodfactors may be due to the absence of a putative cellreception, or receptors, that perceive them, or therepression of Nod signal transduction,or both, inthese cells.

In contrast to Nod factors, chitooligosaccharidealone was found to be inactive in promotingMtENOD12 expression in rice roots. This findingsuggests that the Nod factor-mediated MtENOD12expression in roots is not simply due to the actionof chitooligosaccharides released after degradationof Nod factors by plant enzymes, and that the struc-tural features of Nod factors are clearly responsiblefor eliciting the expression of MtENOD12 in rice.

Taken together, our findings suggest that the ge-netic machinery regulating nodule development inlegumes is at least partially conserved in rice. It is,therefore, essential that future studies be extendedat the cellular and molecular levels to identify whyrhizobia-induced symbiotic responses do not fullyoccur in rice. This could lead to genetically engi-neering rice to form a more intimate symbiotic as-sociation with rhizobia.

Implementing ecoregional approachesto improve natural resource managementin Asia

IRRI, in 1995, accepted the task of leading theecoregional initiative for the humid and subhumidtropics and subtropics. The focus of the ecoregionalapproach is conservation and management of natu-ral resources to develop sustainable food productionsystems, with attention to socioeconomic factors inbiophysically defined ecoregions. In 1998, theecoregional project became part of IRRI’s researchprogram. There have been three major sets of re-search activities:

1. Development of an operational research anddevelopment model for natural resource man-agement (NRM) in a partnership mode in-volving NARS, the international agriculturalresearch centers (IARCs), advanced researchinstitutions (ARIs), and nongovernment orga-nizations (NGOs). The first pilot ecoregionwas established in the Red River Basin in1998.

2. Development of systems approaches andmethodologies● for biotic stress characterization;● assessment of the status of rice demand

and supply, and the relationship betweendemand and use of natural resources; and

● exploring land use options and supportinga network of study sites in different eco-regions in four countries.

3. Developing participatory approaches to NRMfrom field or farm to the regional level andfostering closer linkages between NRM re-search and development efforts in the uplandsof the Red River Basin.

Characterization of tropical lowland riceproduction situations and injury profilesS. Savary, L. Willocquet, F.A. Elazegui, P.S. Teng,and N. Castilla

CHARACTERIZATION: PRODUCTION SITUATIONS

AND INJURY PROFILES

A protocol for characterizing patterns of rice crop-ping practices and injuries due to pathogens, insects,and weeds was used for six tropical Asian sites cov-


ering a wide range of lowland rice environments.Data used were collected from several hundred in-dividual rice fields.

Production situations and injury profiles.Multivariate, nonparametric analysis of the surveydata provides a sound, reasonable basis for charac-terizing the biotic stresses and their effects on riceyields.

A limited number of patterns of cropping prac-tices, as represented by the six production situa-tions, PR1 to PR6, emerge in common across thesurveyed sites. Table 10 summarizes the character-istics of the production situations and the corre-sponding rice yields. The overall mean of farmers’yields was 4.1 t ha-1, which agrees with commonlyreported yields for lowland rice in tropical Asia.

Five injury profiles (IN1 to IN5) were addition-ally identified (Table 11). Figure 14 shows the dis-tribution of production situations at the six surveyedsites. Figure 15 shows that three of the five injuryprofiles are particularly frequent: IN1 (stem rot andsheath blight); IN2 (bacterial leaf blight,

Table 10. Production situationsa (PR1-PR5) for lowland rice characterized across tropical Asia. IRRI, 1998.

PR MF FP WCP IU HU FU DS WE PM PC Y (t ha-1)

PR1 High Long Herb Medium Medium Low Low Low TPR Rice 4.8PR2 Low Long NW Medium Low Low Low Low TPR Rice 4.6PR3 Low Medium Hand Low Low Low High Low TPR W/B 3.5PR4 High Short Hand High High High Low Low TPR W/B 6.7PR5 High Medium Herb Medium Medium High High High DSR Rice 3.8PR6 High Short NW Medium Low High Medium High DSR Rice 3.9

aMineral fertilizer input (MF), fallow period duration preceding the rice crop (FP), weed control practices (WCP), insecticide use (IU), herbicideuse (HU), fungicide use (FU), drought stress (DS), water excess (WE), crop establishment method (PM), crop preceding the rice crop (PC), andmean yield estimated in each cluster of production situations (Y). PRs are described by their predominant characteristics (medians) only,e.g., DSR implies that this is the most frequent crop establishment method in a cluster. Attributes are described with reference to the otherclusters of production situations, e.g., high means that the attribute has a higher median than others in the cluster. For WCP, herb = herbi-cides, hand = hand-weeding, NW = no specific direct weed control measures; for PC, W/B = wheat or barley.

Table 11. Injury profilesa (IN1-IN5) for lowland rice characterized across Asia. IRRI, 1998.

INs BLB SR ShR ShB BS LB NB PH RWM LF DH WH WA WB Y(t ha-1)

IN1 None H L H L None None M H M M M M M 4.6IN2 Present M M L H M L M H H M M H H 3.9IN3 None None H M H H H L H L H H M M 3.5IN4 None None H H M None L L L L L L M H 4.3IN5 None None None None M L None L L H M None L L 3.3

a BLB = bacterial leaf blight, SR = stem rot, ShR = sheath rot, ShB = sheath blight, BS = brown spot, LB = leaf blast, NB = neck blast, PH =planthopper, RWM = rice whorl maggot, LF = leaffolders, DH = deadheart, WH =whitehead, WA = weed infestation above the rice crop canopy,WB = weed infestation below the rice crop canopy, Y = mean yield estimated in each cluster of production situations. INs are described withreference to the other clusters of injury profiles, e.g., high means that the considered attribute has a higher mean in the considered injuryprofile than in the others. L = low, M = medium, H = high.

14. Ecoregional display of production situations derived fromcluster analysis on an array of 15 categorized attributes of thepatterns of cropping practices. The analyses involve severalseasons in six sites: 2 cropping seasons in FAIZ, 2 croppingseasons in CLUZ, 3 cropping seasons in MD, 1 cropping seasonin HGZ, 2 cropping seasons in LAG, and 2 cropping seasons inILO.

FAIZ

HGZ

CLUZ

LAG

ILO

MD

PR1

PR3

PR2

PR4

PR5 PR6


15. Ecoregional display of injury profiles derived from clusteranalysis on an array of 10 quantitative measurements of injurylevels.

planthoppers, and leaffolders); and IN3 (sheath rot,brown spot, leaf blast, and neck blast).

Current importance of rice pest injuries byproduction situations. Certain injury profiles aredistinctly associated with particular production situ-ations at a regional scale (Fig. 16). Production situ-ations PR1, PR2, and PR4, which occur at sitesCLUZ and HG, represent situations where com-paratively high attainable yields may be achieved infavorable irrigated environments. These productionsituations are associated with injury profile IN1,where sheath and stem diseases predominate (Fig.16a). PR3 reflects a poorly endowed, rainfed low-land situation, e.g. at sites FAIZ and ILO, and is as-sociated with injury profiles IN3 and IN4, which arecharacterized by many injuries. PR5 and PR6,which occur at sites MD, LAG, and ILO, arefavorable irrigated environments but with watermanagement problems. The corresponding attain-able yields are average. These production situationsare associated with injury profile IN2.

Injury profiles and yield levels are stronglylinked, but in a complex pattern, suggesting that noone specific injury profile is related per se to thevariation of yield. Therefore, the yield-reducing ef-fect of a given injury profile should be addressed atthe specific scale of a given production situationrather than at the regional level (Fig. 16c). The cor-responding production situations and injury profilesconcur with weather patterns in their description ofvariation in yield levels.

16. Display of linkages between injury profiles IN andproduction situations PR (a); between production situations andincreasing levels of actual, categorized, yield levels Y1 to Y5(b); and between actual yield levels and injury profiles acrossthe region (c), using correspondence analyses.

FAIZ

HGZ

CLUZ

LAG

ILO

MD

IN1

IN3

IN2

IN4

IN5

IN5

IN3

IN1

IN4

IN2

INYY4

Y3Y2

Y1Y5

c

--1 --0.5 0 0 0.5 1Axis 1

PRY

Y2

Y1

Y3 Y4PR1

PR5PR3

Y5

PR6

PR2

PR4b

PR6

PR3

PR5

IN2

IN4 IN3

IN5

IN1

PR1 PR4PR2

INPR

a

Axis 2

1

0.5

0

–0.1

–0.2

1

0.5

0

–0.1

–0.2

1

0.5

0

–0.1

–0.2

Most of the progress in closing the gap betweenactual (4.1 t ha-1) and attainable yield should be ex-pected from better management, especially watersupply. Injuries due to pests should be seen as sec-ondary factors in their yield-reducing effects, com-pared with alleviation of yield-limiting factors.

This approach in characterization enables broaddomains to be identified for pest management strat-egies that are specific to production situationsacross the region.

Linking characterization results with experi-mental yield loss measurements. A series of ex-periments were conducted where injuries due topests (pathogens, insects, and weeds) were manipu-lated at levels of production representing the low-land production situations characterized in the sur-


17. Estimated current yield losses due to selected rice pests in tropical Asia. Average losses (%) due to injuries have been computedunder three scenarios: injuries set at their mean values across the region; injuries set at their median values across the region; injuriesset at published IPM threshold values. Note that the vertical axis is on a logarithmic scale. The 'combined' bars refer to losses due toinjuries combined into regionwide injury profiles based on means, medians, or thresholds.

Mean survey

Median survey

IPM threshold

100

10

1

0.1WB WA WH DH WM BS RTD PB LB BLB SHB Combined

Injuries

Yield losses (%)

vey. A principal component regression model ad-equately described the variation in actual yield (R2

= 0.978; F = 2269; n = 445 plots).The yield-reducing effect of some injuries was

found to vary with changing, e.g. improving, pro-duction situations. For instance, yield reductionsdue to sheath blight, weed infestation, and tungrodisease tend respectively to increase, remain stable,and decrease with increasing attainable yields.Principal component regression allows for estima-tion of yield losses attributable to individual injuries(Fig. 17). The conclusions were:

● Weeds (WA, WB) appear to be the mostimportant constraint across the region.

● Yield losses computed for all injuriescombined do not add up to the losses derivedindividually from each injury, indicating aless-than-additive effect of most injuries onyield losses.

● Losses due to brown spot are high when meansare considered but not so when medians areused. That indicates the importance of thisdisease in some production situations.

● The use of published integrated pestmanagement (IPM) thresholds generallyunderestimates losses caused by most pests.IPM thresholds blatantly exaggerate the

importance of pests when considered in acombined situation.

Our results indicate that sheath blight, brownspot, and leaf blast cause important losses (between1 and 10%) at the regional scale. Among the insectinjuries, only whiteheads caused by stem borers ap-pear to be of relevance (2.3% yield losses). How-ever, these injuries do not match in importance withthose caused by weeds. Both types of injuries dueto weeds, WA and WB, cause about 20% yieldlosses when considered individually. When allmean injuries are combined into a single mean in-jury profile, at a regional attainable yield of 5.5 t ha-

1, a mean yield loss of 37.2 % is estimated.Two other types of injuries need mention. The

first pertains to injuries that are controlled by cur-rent technologies used by farmers, particularly hostplant resistance (e.g., to blast, bacterial leaf blight).The second pertains to injuries caused by harmfulagents that are able to spread over large distancesand cause considerable damage locally (e.g.,tungro). Our results indicate that, regionwide, lossescaused by tungro are low.

The importance of individual pests in the differ-ent injury profiles associated with the six produc-tion situations are summarized in Table 12.


Table 12. Importance of injuries by production situations.IRRI, 1998.

Production Key components of the Importancesituation corresponding of injuries

injury profilesa

PR1 SR MediumPR2 ShB Very highPR4 PH Low

WH HighWA MediumWB Medium

PR3 ShR HighShB MediumBS Very highLB LowNB LowDH HighWH MediumWA MediumWB High

PR5 BLB LowPR6 ShB High

LB MediumPH LowWH MediumWA Very highWB Very high

aSR = stem rot, ShB = sheath blight, PH = planthoppers, WH =whiteheads, WA = weed infestation above the rice crop canopy, WB= weed infestation below the canopy, ShR=sheath rot, BS = brownspot, LB = leaf blast, NB = neck blast, DH = deadhearts, BLB =bacterial leaf blight.

A multiple-pest, production situation-specificmodel to simulate yield losses of rice intropical AsiaL. Willocquet, S. Savary, L. Fernandez, andP.S. Teng

A simple model was developed to simulate riceyield losses due to insects (deadhearts, whiteheads),weeds, and disease (sheath blight) in a range of pro-duction situations, making use of information gen-erated by empirical and mechanistic approachesover the last decade.

MODEL STRUCTURE

The model, which is based on daily time-steps, andconsiders 1 m2 area of rice crop, consists of twolinked components. The first component simulatesthe dynamics of rice biomass, i.e., its daily partition-ing into leaves, stems, roots, and panicles. The sec-ond component simulates the dynamics of tillering,tiller maturation, panicle formation, and tiller death.State variables and simulated processes allow ac-counting for the effects of production situations(i.e., yield-limiting factors) and injuries (i.e., yield-reducing factors) on rice crop growth and yield(Fig. 18).

18. Schematic representation of the rice crop growth model. IRRI, 1998.

Crop biomass component

Growth

Pool ofbiomass

Dry weightof leaves

Dry weightof stems

Dry weightof grains

Dry weightof roots

Dev.stage

Tiller numbercomponent

Number ofvegetativetillers

Number ofreproductivetillers

Coupling point for damage due to pests

Coupling point for the effect of production situation


19. Simulated versus observed yield in a 1997 experiment atIRRI. Each dot represents one injury treatment within oneproduction situation, including the (noninjured) controltreatments. IRRI, 1998.

Coupling functions representing damage mecha-nisms due to stem borers, weeds, and sheath blightwere developed and parameterized using publishedand experimental data. The damage mechanismsconsidered for sheath blight injury were decrease inleaf area index (LAI) and leaf senescence caused byleaf and sheath lesions. Deadheart damage mecha-nism was accounted for as a daily removal of veg-etative tillers, numerically linked with a correspond-ing loss of dry matter of leaves and sheaths. Theoverall, field-level effect of whitehead damage wassimulated as the nonfilling of the injured panicles.

The overall effect of weed infestation is simu-lated by a reduction of rice crop growth, using afunctional relationship between rice growth-rate re-duction factor and weed biomass derived from pub-lished data.

MODEL CALIBRATION AND TESTING

Field experiments were designed whereby, for agiven production situation, rice plots free of pestsand those injured by pests (alone or in combination)are established. Crop growth and yield, environ-mental factors, and pest injuries were monitored.Data from control plots were used to calibrate pa-rameters for attainable yield simulation, while datafrom injured plots were used to test the simulationof yield losses due to pests.

Simulation of attainable and actual yield. Theparameters required to simulate attainable growthand attainable yield were calibrated in three produc-tion situations (PS) in irrigated conditions com-monly found in the Philippines and Vietnam: PS1and PS2 —transplanted rice (IR72) with N fertilizerrates of 30 kg ha-1 and 110 kg ha-1, and PS3—direct-seeded rice with N applied at 60 kg ha-1. The grainyields were respectively 556, 642, and 583 g m-2 forPS1, PS2, and PS3.

Figure 19 shows plots of the simulated againstobserved grain yield for the 18 (PS × injury) combi-nations. Simulated yield estimates falling within±10% of the observed yield were considered accept-able, given that an experimental error of at least10% is usually associated with estimation of riceyields.

In most cases, the damage mechanisms due tosheath blight, deadhearts, whiteheads, weeds, andcombined injuries were well accounted for by themodel, except for four cases—PS1: WD and

COMBI; PS2: WH and COMBI. The poor perform-ance of the model with respect to damage due toweeds in PS1 and to whiteheads in PS2 was re-flected in the two corresponding COMBI treatmentsas well.

Sensitivity analyses. The model calibrated forPS2 was run at four injury levels—no injury, M,2×M, and 4×M, where M corresponds to the meaninjury level across a population of 450 farmers’fields surveyed in tropical Asia. One injury wasconsidered at a time.

Results from sensitivity analyses for varying lev-els of damage are shown in Figure 20. Increasinglevels of sheath blight injury were associated withdecreased LAI, and subsequently decreased dryweight of panicle and yield (Fig. 20a). Sheath blightsimulation resulted in yield losses ranging from 5.7to 24.6%; maximum sheath blight severity hadlosses ranging from 10 to 40%. The simulated yieldloss at mean sheath blight level is similar to that es-timated from empirical experiments. Increasing lev-els of deadheart injury were also associated withdecreased LAI, and subsequently decreased panicledry weight and yield (Fig. 20b), but the effect onLAI and panicle weight was small, e.g., a simulatedyield loss of <1% at the highest level of injury con-sidered. This is in agreement with previous reports,which conclude that deadhearts do not cause severedamage unless a high incidence is reached, and alsoholds true for irrigated, direct-seeded rice with me-dium fertilization. Whitehead injury did not at all

100

600

500

400

300

200

100200 300 400 500 600 700

PS1, COMBI

PS2, COMBI

PS2, WH

PS1, WEED

Y sim

Y obs

Y sim1:1Y obs - (10%*Yobs)Y obs + (10%*Yobs)


20. Simulated LAI and panicle dry weight in a rice crop damaged by injuries at different levels. YLm: simulated relative yield losswhen injury level is set to M; YL2m: simulated relative yield loss when injury level is set to 2xM; YL4m: simulated relative yield losswhen injury level is set to 4xM; SHBf: maximum sheath blight severity; DH: percent of deadhearts; WH: percent of whiteheads; WDf:final weed biomass. IRRI, 1998.

700

600

500

400

300

200

100

0

7

6

5

4

3

2

1

0

Deadhearts

YLm = 0.24%

YL2m = 0.48%

YL4m =0.99%

DH = 0 DH = 2.1 % DH = 4.2 % DH = 8.4 %

b

700

600

500

400

300

200

100

0

7

6

5

4

3

2

1

0

Whiteheads

YLm = 3.20%

YL2m = 6.40%

YL4m = 12.80%

WH = 0 WH = 3.2% WH = 6.4% WH = 12.8%

c

14 18 22 26 30 34 38 42 46 50 54 58 62 66 70 74 78 82 86 90 94 98

700

600

500

400

300

200

100

0

7

6

5

4

3

2

1

0

Weeds

YLm = 22.20%

YL2m = 38.53%

YL4m =59.10%

WDf = 0 WDf = 300 g m-2 WDf =150 g m-2 WDf = 600 g m-2

d

700

600

500

400

300

200

100

0

7

6

5

4

3

2

1

0

LAI PANW (g m-2

)

Sheath blight

YLm = 5.7%

YL2m = 13.4%

YL4m =24.6%

SHBf = 0 SHBf = 10% SHBf = 20% SHBf = 40%

a

Days after crop establishment


affect simulated LAI, and caused proportional-to-injury simulated yield losses (Fig. 20c). Increasedweed infestation levels were associated with lowerLAI and panicle dry weight (Fig. 20d).

The model developed is sufficiently flexible toaccount for diverse production situations and injurymechanisms. In most cases, simulated growth andyield were close to observed values, and fell withinthe acceptance range. Field experiments in the Phil-ippines, India, and China will provide data sets forfurther testing the model under other productionsituations. The model can also be adapted for otherinjuries, such as those due to brown planthopper,bacterial leaf blight, or defoliators.

The Systems Research Network (SysNet) forecoregional land use planningR. Roetter, A. Laborte, C.T. Hoanh, P. Cabrera,C. Lopez, B. Nunez, and P.S. Teng

The Systems Research Network (SysNet) projectstarted in late 1996 with the objectives of develop-ing

● scientific-technical methodology for exploringland use options using crop models and expertsystems, and

● operational methodology for supporting anetwork of sites representing various eco-regions in Asia

SysNet consists of four main NARS partners—In-dia (Indian Agricultural Research Institute), Malay-sia (Malaysian Agricultural Research and Develop-ment Institute), Philippines (University of the Phil-ippines Los Baños, Mariano Marcos State Univer-sity, and PhilRice), and Vietnam (Cuu Long DeltaRice Research Institute)—and IRRI. Collaboratingscientists are from the Wageningen University andResearch Centre, The Netherlands.

SysNet case studies were set up at the subna-tional level in India, Malaysia, Philippines, and Vi-etnam. A common framework and ecoregional ap-proach was adopted that bring together models, ex-pert systems, and multiple-goal analysis to provideland-use options for local problems identified bystakeholders and related to competition for limitedresources. The core of this approach is multiple-goal analysis, which allows one to weigh compet-ing goals of stakeholders in a region.

THE SYSNET METHODOLOGY

The sequence of nine steps for methodology devel-opment followed by SysNet is illustrated in Figure21. In 1998, the project completed the first iterationof testing, generalizing, and refining the Land UsePlanning and Analysis System (LUPAS) for eachcase study (steps 6-8).

LUPAS, designed by SysNet for the purpose ofexploratory land-use analysis, consists of threedatabases and four major components plus geo-graphic information systems (GIS) as a supportivecomponent (Fig. 22). The core of LUPAS is an op-timization model based on the linear programmingtechnique for exploring land-use options. The otherthree components relate to assessment of resourceavailability, estimation of crop yield and livestockproduction, and input-output relations for the vari-ous agricultural production activities.

The starting points for the analysis are policyviews and development plans that are translated intoalternative sets of objectives (scenarios) for a givenregion. Conversion of these objectives into math-ematical equations (objective functions) constitutesthe first step of developing a multiple-goal linear-programming model (MGLP) for quantifying trade-offs among conflicting goals and identifying opti-mum land-use allocation for a given set of objec-tives and constraints.

The generic crop growth simulation model(WOFOST) for annual crops was improved, cali-brated, and evaluated for rice cultivars OM997,IR72, and IR64, among others, in support of yieldestimation.

SysNet case studies. Each of the SysNet studysites has its own set of biophysical and socioeco-nomic characteristics, NRM issues, and regional de-velopment goals, as summarized in Table 13.

Applying the LUPAS methodology. The LUPASmethodology was applied to each of the case stud-ies. Table 14 shows preliminary results based on alimited set of four objectives for Ilocos Norte Prov-ince, Philippines. Two scenarios were considered(no water-sharing and water-sharing) assuming ex-istence of an efficient irrigation network connectingall the municipalities of the province. It was furtherassumed that alternative production technologywith higher resource-use efficiency than the current


22. Components of the Land Use Planning and Analysis System (LUPAS). IRRI, 1998.

21. Steps in SysNet methodology development. IRRI, 1998.

Learning from NARSand stakeholders

Outline LUPAS structure

Collecting and processing data

Training NARS on LUPAScomponents

Integrating LUPAS componentsby NARS and stakeholders

Testing the LUPAS with NARSand stakeholders

Generalizing and tailoring theLUPAS to case studies

Refining the LUPAS for eachcase study

Validating and continuing present casestudies and starting new case studies9)

8)

7)

6)

5)

4)

3)

2)

1)New case study with:-new approach and/or-new region

Itera

tive

proc

ess

Data on bio-physical

resources

Data on socio-economicresources

RESOURCEBALANCEAND LAND

EVALUATION

INPUT /OUTPUT

ESTIMATION

INTERACTIVEMULTIPLE GOAL

LINEARPROGRAMMING

Land useoptions and

achieve-ments

Data onpolicy views and

developmentplans

YIELDESTIMATION

GIS


Table 13. Natural resource management (NRM) issues and regional development goals of the SysNet sites. IRRI, 1998.

SysNet site NRM issues Regional development goals

Haryana State, Lowering of water table in the Intensify cereal production. Solve water India northeast. problems. Manage salinization Increase

Waterlogging, flooding, and farmers’ income. salinization in the central part.Rural-urban migration due to low farm incomes.

Kedah-Perlis region, Malaysia Competition for agricultural land from Intensify and increase rice production. urban and industrial expansion. Increase nonfood production. IncreaseReduced farm labor. Federal policy for labor use efficiency. Reduce use of the region to remain as the country’s agrochemicals by improving resource rice bowl. use efficiency. Increase farmers’ income.

Ilocos Norte Province, Philippines High diversification of dry season Intensify rice production Increase cash cropping. crop production. Increase employment inHigh use of agricultural chemicals agriculture. Increase input use efficiency. and water in dry season. Increase farmers’ income.Upland cultivation on steep slopes, causing soil erosion. Leaching– groundwater pollution by nitrate and biocide residues. Conversion of agricultural land for urban use.

Can Tho Province, Vietnam Intensification of rice cropping. Intensify and increase rice production.Crop diversification. Diversify agriculture. Increase farmers’Farmers’ and policymakers’ income. development objectives are at variance.

Table 14. Example of MGLP outputs, Ilocos Norte Province, Philippines: goal achievements without and with watersharing.

Maximize rice Maximize other Maximize MaximizeNo. Goal production production employment income

(A) (B) (C) (D)

Without water sharing1 Rice production (t) 620,088 147,414 335,376 138,7972 Other production (t) 50,876 1,868,771 597,226 1,412,6443 Employment (mandays) 10,135,591 6,907,862 11,953,708 6,300,5374 Total income (000 P) 5,798,165 13,010,818 9,268,957 31,557,859

With water sharing1 Rice production (t) 887,230 156,059 382,201 218,5932 Other production (t) 0 2,448,860 938,753 2,009,0683 Employment (mandays) 12,551,854 8,294,347 15,553,056 9,346,4364 Total income (000 P) 7,299,089 16,206,893 13,375,791 39,083,256

farmers’ practices will be available in the future.Model results are presented for the zero round, i.e.,a model run that optimizes individual goals withoutimposing restrictions set by minimum requirementsfor satisfying other goals. Results with both sce-narios indicate that farmers’ income will be lowest

if the province opts for maximizing rice production.Incomes will be highest by allocating more land forcultivating the more profitable crops such as garlic,tomato, and onion. Effective water-sharing wouldincrease individual goal achievements by 20-30%.

=

=


Progress of unreported projects

Rice—a way of life for the next generation ofrice farmersM. Bell

● Through a multisectoral international thinktank, developed an R&D approach for in-creasing the impact of engineering in agri-cultural and rural development.

● Facilitated a postproduction chain stake-holders meeting in the Philippines. Identifiedneeds, concerns, and opportunities within thepostproduction industry in the Philippines anda greater understanding of the wider series ofissues for all participants. This meeting led tothe formation of the Philippine Rice Post-production Consortium (consisting of theNFA, BPRE, CEAT/UPLB, PhilRice, andIRRI).

● Organized multisectoral stakeholders’meetings and formalized partnership modesfor improved dissemination channels tofarmers through NARS and NGOs in Thailandand Bangladesh. Identified key agronomiclimitations in northeast Thailand and engineer-ing limitations in Bangladesh. Trained ThaiNGO collaborators in rice production princi-ples. Have observed large buy-in to the con-cept of multisectoral partnerships.

● Defined components of yield gap project inBangladesh. Designed questionnaires forsurveys and conducted data collectiontraining. Began surveys for the rapid ruralappraisal for general characterization of eightvillages in Bangladesh. Will use results toidentify farm households for the intensivesurvey and to estimate technical efficiencydifferentiation across farms.

● Established field demonstrations involvingNGO, government, and IRRI-Rainfed Low-land Rice Research Consortium for promotionto farmers (short-maturity rice-chickpea rota-tion in Bangladesh, and leveling, improvednutrition, and weed management in northeastThailand). Participated in successful NGO-NARS field day, which highlighted the suc-cessful outcome of selected technologies inThailand. The number of farmers interested in

the technologies for 1999 has increasedtenfold.

● Information technology—developed knowl-edge packages on technology change options.Developed, field tested, and identified im-provements for the draft “TropRice” decisionsupport system. Developed and placed on theIRRI intranet a Web site about IRRIengineering technology.

● Published proceedings of engineering thinktank, promoted the recommended approachthrough several journals and newsletters, andgave five presentations in various internationalvenues.

● Facilitated the availability for demonstrationof the improved SG800. Completed and madeavailable the blueprints for the strippergatherer SG800 Mk III.

● Developed databases of drying systems, trans-planters, hand tractors, power tillers, andcombine harvesters available in the market,including their features, capacity, cost, andmanufacturers.

● Began evaluating impact of introduced post-harvest machinery (rice flour mill, rice de-huller for glutinous rice processing, and porta-ble rice micromill) on family welfare andwomen’s groups.

● Completed the IRRI component of the ImpactAssessment and Evaluation Group (IAEG)project on “CGIAR and NARS PostproductionInnovations in the Philippines and Vietnam.”Produced a video titled Fertile Feedback:Postharvest Innovations through Partnershipsto demonstrate that the impact of public-sectorR&D can be accelerated by research partner-ships with manufacturers and users.

● Began case study in Thailand to look at theeffectiveness of the multisectoral approach toknowledge transfer. Identified relevant datasources.

● Conducted basic experiments on the effects ofvariety, drying air temperature, and relativehumidity on fissuring, milling quality, anddrying performance. Developed low-costlaboratory equipment especially for studyingrice fissuring for drying and readsorptionfissuring studies and training.


● Tested the stripper combine SC1500 duringthe 1998 DS. Shattering loss was recorded atabout 1.6%, at a forward speed of about 4 kph.

● Tested and optimized the biomass-sensor“pendulum-meter” in drum-seeded IR72 ricefor in-field, site-specific use at mid-tillering,booting, and milky grain stages.

● Parameterized and validated two tilleringmodels and compared them with a newlydeveloped tiller model based on relative cropgrowth rate.

Socioeconomic studies for technologyimpact, gender, and policy analysisM. Hossain

● Updated world rice statistics database to 1997.● Began integration of biophysical and socio-

economic variables at subnational levels forBangladesh and Myanmar.

● Prepared a manuscript, A Rice Village Saga:The Three Decades of Green Revolution in thePhilippines (by Y. Hayami and M. Kikuchi)for copublication by Macmillan Press andIRRI.

● Analyzed the Central Luzon and Laguna long-term household survey data and prepared aresearch monograph for publication in 1999,which highlights the evolution of rice produc-tion technologies and their impact on the ruralhousehold economy. With these new techno-logies, the Philippines strengthened its compa-rative advantage in rice cultivation from 1966to 1979. But this advantage began eroding in1986 because of the decline in the world priceof rice, stagnating yield, and higher prices ofland and labor. By 1994, the country had lostits comparative advantage.

● Assessed changes in the rural householdeconomy for 1987 and 1995 for Thailand.

● Surveyed eight villages in Bihar, India, tounderstand the importance of rice in thehousehold economy and to analyze constraintsto the adoption of new technologies.

● Processed in electronic files household surveydata for four villages in Myanmar and sixvillages in eastern Uttar Pradesh.

● Completed a study for Vietnam on the impactof modern rice varieties on rice productivity,

socioeconomic equity, and poverty, whichshowed that the adoption of modern ricevarieties was almost complete in villages withaccess to physical infrastructure and irrigationfacilities. Their adoption contributed to analmost 20% reduction in the unit cost of riceproduction. Their adoption has also helped toalleviate poverty and better distribute ruralincomes because of the more equaldistribution of landholding and absence ofcrop-sharing tenancy.

● Generated information on the impact ofbreeding strategies on the diversity of ricecultivars through household surveys inMadhya Pradesh and Uttar Pradesh (India),Bangladesh, and the Philippines.

● Began a survey for updating IRRI’s databaseon the release of rice varieties and theirgenealogy.

● Published a book, Impact of Rice Research(edited by Pingali and Hossain), emanatingfrom the international conference of the samename held in Bangkok, 3-5 Jun 1996.

Program outlook

Research activities under the program for 1999 willfocus on

● linking gene function to molecular map andgenomic sequences;

● transferring resistance against brownplanthopper to elite lines;

● developing tolerance for stem borer and gallmidge in collaboration with NARS partners;

● transferring disease resistance and tolerancefor adverse soil conditions from wild speciesto rice;

● implementing MAS to transfer multiple-disease resistance genes to elite cultivars;

● developing a model for sheath blightmanagement and for deploying biocontrolagents for diseases;

● developing strategies for field testing oftransgenic plants, using the endogenousresistance gene Xa21 as a case study;

● analyzing factors that contribute to yield gaps;● using information technology tools for

knowledge packaging and for demonstratingtechnology options for farmers;


● generating land-use options for selected sitesto demonstrate sustainable NRM at regionallevels;

● assessing economic values of IRRI’sgermplasm-related research, analyzinghousehold-level data to assess the impact ofbreeding strategies on the biodiversity of ricecultivars; and

● evaluating impact of improved ricetechnologies on income distribution andpoverty in the Philippines.

In addition to these focused research activities,the Cross Ecosystems Research Program has initi-ated a new Functional Genomics project to be fullyimplemented in 2000. The overall goal of thisproject is to develop genetic resources and researchcapacity to apply information and reagents provided

by structural genomics to understand complex bio-logical functions. A genomewide experimental ap-proach will help IRRI find new genes and dissectmetabolic pathways important for increasing riceproductivity. By creating genetic resources for traitdiscovery, IRRI can be in a strong position to usethe vast genomics databases and to ensure accessi-bility of these resources to the rice-growing world.

In 1999, we have defined the scope and activi-ties of the project and have made progress in pre-paring the genetic resources (mutants, isogeniclines, mapping populations) essential for functionalgenomics. We have also explored partnerships withboth private and public sectors. We expect theFunctional Genomics project to become the enginefor trait discovery and synthesis that can be used byecosystem-based programs for solving specific pro-duction constraints.

Rice genetic resources: conservation, safe delivery, and use 123

Research programsRice genetic resources: conservation, safe delivery, and use

CONSERVATION OF RICE AND BIOFERTILIZER GENETIC RESOURCES 124Germplasm and information exchange 124Genebank management 126Germplasm characterization 126Data management 127Training 127Conservation of biofertilizer germplasm 128Biosystematic studies of wild rices 129Dynamic systems of genetic conservation 129

DELIVERY OF GENETIC RESOURCES: THE INTERNATIONAL NETWORK FOR GENETIC EVALUATIONOF RICE (INGER) 1301998 INGER nurseries 130Processing and distribution of test materials for the Upland Rice Research Consortium and Breeding Network 130Additional seed distribution 131Seed increase for INGER nurseries 131Preparation of the 1999 INGER nurseries 131Utilization of the 1997 INGER entries 131

THE INTERNATIONAL RICE INFORMATION SYSTEM 131The Genealogy Management System 131The Data Management System 132ICIS applications 133Linkages 133

SEED HEALTH TESTING SERVICES 133

PROGRAM OUTLOOK 135


The IRRI Medium-term Plan for 1998-2003 con-solidated genetic resources activities into fourprojects in this new program. It contains research-support and research components of germplasmconservation and evaluation, as well as seed healthactivities. Studies on the biosystematic relationshipsof the genus Oryza are included. A new project fordevelopment of the International Rice InformationSystem (IRIS), which is part of a broader databasedevelopment agenda between IRRI and the Interna-tional Maize and Wheat Improvement Center(CIMMYT), is also included.

Conservation of rice and biofertilizergenetic resources

Germplasm and information exchangeM.T. Jackson, B.R. Lu, G.C. Loresto, andS. Appa Rao

More than 8,150 samples of Oryza sativa (7,409)and various wild species (745) were received from16 countries for long-term conservation in the Inter-national Rice Genebank. Much of that germplasmwas collected by partner national agricultural re-search systems (NARS).

BANGLADESH

B.R. Lu assisted genebank staff members of theBangladesh Rice Research Institute to collect wildspecies in the southern and western districts. Tensamples were collected. Only one wild species, O.rufipogon, one weedy type, and two related genera,Hygroryza aristata and Leersia species, werefound. Farmers reported that wild types were more

Rice genetic resources: conservation, safe delivery,and use

common 5-10 yr ago. Factors that contributed togenetic erosion are 1) rapid change of the rice eco-system from deepwater rice to irrigated rice (boro),2) extensive human disturbance of wild rice habi-tats, 3) intensive culture of fish, 4) intensive cattlegrazing and harvesting of grasses for cattle feed,and 5) overexploitation of agricultural land.

BHUTAN

Extension staff members trained by IRRI collectedmore than 50 samples of cultivated rice in west cen-tral Bhutan. Some 255 samples of cultivated ricecollected in eastern Bhutan were multiplied at theRenewable Natural Resources Research Centre,Bajothang.

CAMBODIA

Extension workers collected 438 samples of wildspecies in seven provinces and 298 samples of cul-tivated rice in three provinces between Dec 1997and Feb 1998. One extension worker in Stung Trengtook the initiative of collecting 31 samples of tradi-tional varieties in an area formerly held by theKhmer Rouge. IRRI received 620 samples of wildspecies and 492 samples of cultivated traditionalvarieties for long-term storage.

COSTA RICA

New areas along the Atlantic coast, from the Colo-rado River to Manzanillo, were identified for col-lecting O. latifolia. Plants and insects associatedwith wild Oryza and information of water and soilswere also collected. The O. latifolia samples were


characterized and a morphological analysis made. Adetailed study of a population of O. glumaepatulafrom Rio Medio Queso (near the frontier with Nica-ragua) is ongoing.

INDONESIA

Almost 300 samples collected from Aceh inSumatra and in central Kalimantan were received atIRRI for long-term conservation. B.R. Lu helpedIndonesian colleagues collect wild rices in centralSulawesi. The group found a population of O.meyeriana completely shaded under trees in amountainous area, the first reported collection ofthis species in central Sulawesi. Local farmers referto it as padi kakaju (forest chicken rice). Thirty-twoupland and lowland rices were also collected.

LAO PDR

S.A. Rao collaborated with extension personnel andMinistry of Agriculture and Forestry officials tocollect more than 2,150 samples of cultivated riceand eight wild species from the southern regionsand northern provinces. More than 3,870 samples ofcultivated rice and 29 samples of wild species werereceived at IRRI. The Lao rice collection is the sec-ond largest component in the International RiceGenebank.

MADAGASCAR

Collecting activities during the second quarter of1998 were part of training for field collection. Oneof the highlights of field training was the collectionof natural hybrids between O. longistaminata andO. sativa. Research staff members also collected 30samples from the middle-west area. Duplicates ofone O. longistaminata and 151 samples of culti-vated rice were received at IRRI for long-term con-servation.

MALAYSIA

Collection at an upland area in Sri Aman in Jan1998 was part of a short course on field collectionof rice germplasm for research and extension staffmembers of the Department of Agriculture of Sabahand Sarawak. The rice crop was ready for harvest at

the time of the visit. No one was allowed to gatherseeds or panicle samples from the field because thefarmers had not performed their rice harvest rituals.However, some farmers provided one or two pani-cles per variety.

Twenty-one distinct varieties were collected.Farmers grow from five to seven varieties in onefield. Seeds and vegetative stocks of O. officinaliswere also collected in Tijirak village, about 25 kmfrom Kuching. Villagers called this species padipipit, meaning bird rice.

Extension workers and staff members from theMalaysian Agriculture and Research DevelopmentInstitute (MARDI), Seberang Perai, collected 260samples of cultivated rice in the interior of Sibu,Sarawak. During the year, a total of 315 samples ofcultivated rice and 4 samples of O. officinalis werecollected.

MOZAMBIQUE

An Instituto Nacional de Investigaçäo Agronómica(INIA) team collected 72 accessions of cultivatedrices at 23 sampling sites. The samples were highlyvariable, with outstanding traits such as flood toler-ance, low water requirement, aromatic, lodging re-sistance, tolerance for attacks of birds, long grain,early maturity, and high yield.

Eleven accessions of O. longistaminata werealso collected. One accession was an apparent hy-brid between O. longistaminata and O. sativa. Her-barium specimens of the wild species were made.

MYANMAR

Extension workers from Shan, Chin, Kachin, andRakhine states collected 693 samples. About 70%of those were sent to IRRI. More than 210 samplesare currently being multiplied at the Central Agri-cultural Research Institute (CARI), Yezin. Fortysamples of wild species were collected in Dec 1998.

NAMIBIA

The curator of the National Plant Genetic ResourcesCenter (NPGRC) sent five samples of O.longistaminata to IRRI for seed multiplication andconservation. Those samples were collected fromOshana, Omusati, and Oshikoto north-central Na-


mibia. After seed multiplication, IRRI will return aset of samples to NPGRC and the Southern AfricanDevelopment Community (SADC) Plant GeneticResources Center in Zambia.

NEPAL

B. R. Lu assisted national genebank staff memberswith collection of wild rices in the central and west-ern regions. The team collected 73 samples of wildspecies and 2 samples of cultivated rices. About 50ha of pure O. rufipogon were found near AjigaraLake, Kapilbastu District. Populations of O. rufi-pogon and O. nivara were abundant in the lowerTerai region near the Indian border, and O. granu-lata thrives in the evergreen forest at an elevationof 400-500 m.

PHILIPPINES

A collecting team from the Philippine Rice Re-search Institute (PhilRice) invited B.R. Lu to jointhem in collecting wild rice species in the mountain-ous regions of Palawan. The team collected fivesamples of O. meyeriana, known locally as peacockrice because farmers use it as bait for trapping pea-cocks. Farmers also use the roots and undergroundparts of O. meyeriana to cure diarrhea and stomachache. The Philippine team collected 264 samples ofcultivated rice in Surigao, Abra, and Quirino prov-inces. About 190 samples of cultivated rice weresent to IRRI for long-term storage.

THAILAND

Collaborators sent IRRI 200 samples of cultivatedlocal varieties collected in 1997. Collecting activi-ties for 1998 concentrated in the upland areas of thenorth and northeast. About 240 samples of culti-vated and 20 wild rices were collected.

VIETNAM

Collection work in March was part of a short train-ing course on field collection. About 16 upland and2 lowland local cultivars were collected in remotevillages of the mountainous central region. A veg-etative stock of O. rufipogon was collected at theedge of a farmer’s field in an irrigated area. Farm-ers called this species co lung, meaning cattle feed.

A total of 232 samples of cultivated rice were col-lected during 1998. IRRI received 723 samples col-lected in 1995 and 1996 for long-term conservation.

UGANDA

IRRI received nine samples of wild species col-lected in 1997.

Genebank managementM.T. Jackson, F. de Guzman, R. Reaño, andS. Almazan

Germplasm multiplication and rejuvenation activi-ties encompassed 2,080 new introductions of O.sativa, and 3,480 O. sativa accessions alreadystored in the genebank collection. Seed from almost85% of the newly received samples was harvestedfor long-term storage. Samples (439) of wild spe-cies were successfully multiplied in the genebankscreenhouses. Most of the samples were receivedduring the year, including one new species, O.neocaledonica. Protocols were modified for manag-ing accessions of the allozamous African wild ricespecies, O. longistaminata.

We added 4,758 accessions to the Base Collec-tion. The seed viability of about 15,000 accessionsin the Active Collection was monitored (6 yr afterthe previous germination test). In addition, initialviability was determined for about 5,700 samplesthat had been prepared for long-term storage.

Under the terms of the Memorandum of Under-standing (No. 58-5402-8M-F063) with the UnitedStates Department of Agriculture-Agricultural Re-search Service, which was renewed in Sep 1998, anadditional 12,108 samples were sent for black-boxduplicate storage at the National Seed StorageLaboratory, Fort Collins, Colorado.

Germplasm characterizationM.T. Jackson, R. Reaño, and S. Almazan

Vegetative and reproductive characters were scoredduring 1998 wet season (WS) for about 1,700 acces-sions of O. sativa and 190 accessions of O.glaberrima. Postharvest characterization was com-pleted on 1,000 accessions that had been grown dur-ing 1997 WS. Wild species accessions (418) werealso characterized.


Data managementM.T. Jackson, A.P. Alcantara, and E. B. Guevarra

The International Rice Genebank Collection Infor-mation System (IRGCIS) was fully operational.Two powerful servers (with data backup capabili-ties) were acquired to separately house the IRGCISdatabase and application. In terms of data mainte-nance, 27 batches comprising 9,206 samples wereadded to the system, and morphoagronomic data on7,176 accessions were encoded.

The Systemwide Information Network for Ge-netic Resources (SINGER) database provides a sub-set of IRGCIS data, and is accessible through theInternet (http://www.cgiar.org/singer). Data onmore than 82,650 accessions were refreshed inSINGER in February.

TrainingG.C. Loresto, S. Appa Rao, B.R. Lu, andM.T. Jackson

Through support from the Swiss Agency for Devel-opment and Cooperation (SDC), GRC offered in-country training courses as well as on-the-job train-ing at IRRI in field collection techniques, data man-agement, genetic resources conservation and man-agement, and isozyme analysis.

BHUTAN

A 1-wk course on germplasm collection and conser-vation was given at Tingtibi, Zhemgang, to 17 ex-tension and research workers from the east-centralregion—Shemgang, Trongsa, and Gaylegphug dis-tricts. Because access to those areas is difficult andrequires several weeks of trekking, the trained ex-tension and research personnel assigned to the areaswill facilitate the collection of rice germplasm. It isanticipated that extension agents assigned in the re-mote areas near the border with India will be able tofind and collect any wild species that may occur inBhutan.

CAMBODIA

A 2-wk short course on data management was con-ducted at the Cambodia-IRRI Australia Project(CIAP) office in Phnom Penh 26 Feb–6 Mar. One

trainee was a lecturer in the Royal University ofAgriculture, three trainees were from the TechnicalOffice of the Department of Agronomy, and sevenwere from CIAP.

The data management staff at IRRI developedthe Cambodia Rice Information System (CamRIS)for managing the Cambodian rice collections. TheIRRI staff also discussed the use, modification, andenhancement of CamRIS, and the management ofexisting data of the Cambodian rice collection.

INDIA

A short course on data management and documen-tation for 17 genetic resources staff members washeld at the National Bureau of Plant Genetic Re-sources (NBPGR), New Delhi, 26 Oct-7 Nov. Eachparticipant used their own germplasm data to designand develop an information system in MicrosoftAccess 7. Most of them handled multiple crop data.

GRC data management staff members visited thegenebank at the International Crops Research Insti-tute for the Semi-Arid Tropics (ICRISAT) to assistscientists in refining their germplasm databases.

LAO PDR

A training course on field collection for 23 agricul-tural extension officials was held 21-26 Sep at theNorthern Regional Agricultural Station, HouayKhot, Luang Prabang. After the training, extensionpersonnel and the Lao collection team collectedearly-maturing varieties in the northern provinces.

MADAGASCAR

An in-country training on field collection 20-28 Aprat Mandriambero had 12 participants. Three wereextension workers of the Ministry of Agriculturewhile the others were technicians from the NationalCenter for Applied Research on Rural Development(FOFIFA) research stations where collection wasplanned for 1998-99.

A 2-d on-the-job training on field characteriza-tion was held at the Mahitsy Research Station. Atechnician from FOFIFA who had on-the-job train-ing at IRRI served as resource person and super-vised the trainees—eight technicians who partici-pated in the 1997 short course in Mahajanga, and


one plant breeder from Marovoay Research Station.Those trainees joined the 1998 field collection train-ees to share their experiences with the group.

MALAYSIA

A short course on field collection of rice germplasmwas held 16-23 Feb at the Agriculture Institute,Sarawak. Participants were from Sabah (5),Sarawak (14), and Penang (1). Field practicals wereorganized in villages in Kuching, Sebangkoi,Betong, and Sri Aman. The Iban tribes grow mostlyupland varieties in those areas. Samples collectedduring the field practicals were divided into twoportions. One set with the corresponding passportdata was brought to the MARDI genebank atSeberang Perai, and the other set was left in theAgriculture Research Center as part of their work-ing collection. MARDI will multiply the samplesand send duplicates to IRRI. One of the highlightsof the course was the planning session wherein theparticipants were grouped according to their prox-imity to each other and assigned a priority area forcollection. That session established priorities for1998-99 collecting activities in Sabah and Sarawak.

MYANMAR

Training at the Central Agricultural Developmentand Training Center, 14-19 Sep had 23 extensionworkers from Kayah, Kayin, and Tanintharyi statesand 4 research staff members from the CARI seedbank as participants. Extension workers collect inthe remote villages, and the CARI researchers co-ordinate and gather the collected samples alongwith the corresponding information from the differ-ent townships.

VIETNAM

A 9-d course was conducted 16-24 Mar for 15 re-search and extension service staff members at theAgricultural Research Center for Coastal SouthernCentral Vietnam. Field practicals were conducted inremote villages of the Ba Na and U’re tribes. Thoseminority groups grow traditional varieties in theupland and mountainous areas. The participants col-lected 16 upland varieties and two lowland varietieswith their corresponding passport data.

ON-THE-JOB TRAINING

Three research staff members from the China Na-tional Rice Research Institute (CNRRI) and the Chi-nese Academy of Agricultural Sciences (CAAS),and one from PhilRice attended a 3-wk on-the-jobtraining on genetic resources conservation and man-agement 10 Aug-4 Sep. The Chinese researchersalso studied the morphological variation of threespecies using herbarium specimens.

Three Indonesian research staff members fromthe Research Institute for Food Crop Biotechnol-ogy, Bogor, Indonesia, and one from PhilRice weretrained in data management and documentation7-23 Sep. The trainees used data from their insti-tutes to develop prototype rice information systems.

A Vietnamese researcher from the Cuu LongDelta Rice Research Institute underwent a 2-mo on-the-job training on isozyme analysis. A researcherfrom the Vietnam Agricultural Science Institute(VASI) received on-the-job training on isozymeanalysis.

Conservation of biofertilizer germplasmJ.K. Ladha and T. S. Ventura

The biofertilizer germplasm collection at IRRI has1,392 accessions of Azolla, N2-fixing bacteria,Rhizobium sp., cyanobacteria, and aquatic legumespecies. The collection is held by the Soil and Wa-ter Sciences Division. The Azolla collection ismaintained as shoot-tip and liquid cultures, thecyanobacteria on agar slants, and the bacterialstrains by lyophilization, deep freeze, or as agarslants. The aquatic legumes are conserved as seeds.Researchers in 18 countries requested a total of 230samples during 1998.

Management of the biofertilizer collection wasenhanced by work on development of theBiofertilizer Information System (BIOFIS), whichis scheduled for completion in 1999. Data standardswere brought into line with other centers holdingN2-fixing microorganisms, to permit the develop-ment of a CGIAR systemwide database, under theauspices of the Systemwide Genetic Resources Pro-gram (SGRP) and coordinated by the InternationalCenter for Agricultural Research in the Dry Areas(ICARDA).


Biosystematic studies of wild ricesB.R. Lu, M.T. Jackson, A. Juliano, andM.E. Naredo

Chromosome counts of all wild rice species in O.officinalis, O. ridleyi, and O. meyeriana complexesand accessions in O. brachyantha were completed.About 33% of wild rice accessions in the Interna-tional Rice Genebank collection have chromosomecounts.

The diversity of 34 accessions of the Australianwild rice O. meridionalis was studied using mor-phology and isozymes. The accessions fromQueensland generally showed a pattern differentthan the accessions from Northern Territory andWestern Australia.

The genetic diversity of 52 accessions of the Af-rican wild rice O. barthii from 14 countries was es-timated through morphological, isozyme and ran-dom amplified polymorphic DNA (RAPD) studies.Cluster analyses of morphological data and RAPDmarkers revealed one accession from Niger asclearly different from the others. The 52 accessionswere polymorphic for 14 (70%) of the 20 isozymeloci examined. Cluster analysis of these datashowed a tight grouping of 48 accessions, and fouraccessions that formed a distinct cluster at a simi-larity level of 0.87.

O. barthii was hybridized with other AA genomeOryza species, and more than 29,100 spikelets pol-linated. Hybrids between O. barthii/O. barthii andO. barthii/O. glaberrima showed fertility higherthan 70%. Among the other interspecific hybrids,only those with O. longistaminata showed higherthan 5% fertility. Hybrids with O. meridionalisshowed the lowest fertility (<0.2%). These resultsdemonstrate the strong reproductive barriers be-tween O. barthii and the other AA genome wildrices.

Meiotic analysis of O. barthii and its intra- andinterspecific hybrids was undertaken at metaphaseI in the pollen mother cells. All samples showedregular meiosis and high chromosome pairing,which was not significantly lower than in the re-spective parental species. That indicated that thegenome of O. barthii has not become significantlydifferentiated from the other wild rice species stud-ied. However, strong reproductive barriers have de-veloped between these species.

Meiotic pairing of O. ridleyi and O. longiglumis,and their intra- and interspecific hybrids wasanalyzed at metaphase I in pollen mother cells. Allhad regular meioses with full pairing, indicatinghigh chromosome homology among the two spe-cies.

Dynamic systems of genetic conservationJ.L. Pham, S.R. Morin, M. Calibo, S. Quilloy, andM. Bellon

Seed collections and socioeconomic surveys werecompleted in India in partnership with the IndiraGandhi Agricultural University and the NBPGR(New Delhi).

The analysis of the passport data from the seedcollection on the Bastar Plateau (Madhya Pradesh,India) demonstrated the high diversity of rice varie-ties in the region. Among the 106 variety namesfound in the region, 12 account for 50% of the totalnumber of samples collected, and 36 for 80% of thesamples.

Socioeconomic surveys showed that farmers inthe Bastar Plateau and Chhatisgarh areas choose va-rieties based on the interplay between soil qualityand fertility, slope, erratic rainfall patterns, and ba-sic household needs. The outcome is a complex,well-understood system of matching specific varie-ties with soil and plot types (and with other varie-ties) that reduces risk and enhances household wel-fare.

A database of the results from the socioeconomicsurvey in the rainfed lowland system was developedin the Philippines in partnership with PhilRice. Theanalysis of microsatellite polymorphism of 178 ac-cessions from the Cagayan Valley confirmed earlierisozyme data, and the original contribution of theWagwag varieties to the overall diversity of the re-gion. It also showed that traditional varieties are animportant component of the on-farm diversity inthis area as they contain a number of alleles, whichare not present in the modern varieties cultivated inthe region. Thus, 12 microsatellite alleles were spe-cific to the 67 samples of traditional varieties stud-ied, while only 2 alleles were specific to the 111samples of modern varieties.

The analysis of the variety naming process in theCagayan Valley was completed. It showed thatfarmers categorize varieties in a limited number of


groups, which helps them manage varietal diversity.Duration is one of the main criteria used by farm-ers. Variety names change, and those changes alsoindicate genetic changes.

IRRI and PhilRice organized the distribution ofrice seeds to the Cagayan farmers who had contrib-uted to the surveys. About 2 t of seeds representing20 modern and 8 traditional varieties were distrib-uted. Due to El Niño in 1997, typhoon Loleng in1998, and low seed storage capacity, a number offarmers totally lost their own seed, making this op-eration highly appreciated. Farmers were askedwhich varieties they were currently growing, as wellas for the previous three seasons, to evaluate theirchanges since a 1997 survey. A clear trend towardmodern varieties was observed.

In Vietnam, in partnership with the Huê Univer-sity of Agriculture and Forestry, seed collection anda socioeconomic survey were completed in the up-land and irrigated ecosystems. In the four irrigatedvillages, 69 rice samples, representing 17 varietynames, were collected. Seventy samples, represent-ing 17 variety names, were collected in five uplandvillages. Duplicate samples were sent to VASI, Ha-noi.

A field trial in Huê was conducted to study sam-ples collected at the end of the winter crop season1995-96. A field trial at IRRI allowed study of thesamples from the 1996 summer crop season. Analy-sis of the microsatellite polymorphism was com-pleted at IRRI for 77 accessions from the rainfedlowland ecosystem.

Vietnamese scientists completed the secondphase of a biotic survey in the rainfed-lowland eco-system. Analysis of the results of the first phasedemonstrated the difference in the biotic environ-ment between the coastal and inland sites. Encod-ing of the data from the socioeconomic surveys inthe rainfed lowland ecosystem was completed.

Delivery of genetic resources: TheInternational Network for GeneticEvaluation of Rice (INGER)

1998 INGER nurseriesS.W. Ahn, C. Toledo, V. Lopez, and R. Reaño

More than 800 diverse entries from various NARSand international agricultural research centers wereorganized into 10 INGER nurseries. Five ecosys-

tem-oriented trials were planned with an augmentedblock design to assess adaptability to irrigated, up-land, rainfed lowland, upland, and deepwater envi-ronments. Nurseries for multilocation evaluation ofhybrid rice and fine-grained aromatic rice were alsoorganized. Stress-oriented nurseries were composedto screen for soil salinity-alkalinity tolerance andresistance to rice blast and tungro.

DISTRIBUTION

Two hundred and fifty-eight nursery sets were dis-patched to 28 countries. More than 88% of the setswent to countries in Asia, and the remaining 12% tocountries in Sub-Saharan Africa, Latin America,and Europe. Within Asia, South and Southeast Asiareceived 78% of the INGER nurseries. More than700 INGER entries were sent to national programsof Indonesia, Myanmar, Philippines, Thailand,Bangladesh, and India for evaluation and use.

EVALUATION

The ecosystem-oriented nurseries were tested at keytest sites and the stress-oriented nurseries wereevaluated at hot spots for rice blast and tungro. Themost widely tested nurseries were the irrigated ob-servational nursery (IIRON), evaluated at 48 testsites in 26 countries, and blast (IRBN) screeningconducted at 42 sites in 24 countries. Except for therainfed lowland observational nursery (IDRON)and tungro sets, the nurseries were generally as-sessed at more than 20 experimental sites world-wide.

Processing and distribution of test materialsfor the Upland Rice Research Consortiumand Breeding NetworkB. Courtois, S.W. Ahn, and M. Laza

In collaboration with the IRRI Plant Breeding, Ge-netics, and Biochemistry Division (PBGB) and net-work cooperators, 119 upland rice breeding linesfrom China, Indonesia, Myanmar, Bangladesh, Bra-zil, and IRRI were tested for viability, cleaned, andtreated with chemicals to meet quality and quaran-tine requirements. Eight test sets were dispatched toIndonesia, Thailand, Vietnam, Philippines, China,Myanmar, and India for evaluation.


Additional seed distribution

Rice scientists worldwide requested 608 seed sam-ples, which were processed and distributed to 23countries. The best entries in various ecosystems,sources of resistance to pests and diseases, or dif-ferential varieties for insect pests and diseases weremost frequently requested.

Seed increase for INGER nurseries

Seven hundred and twenty-one entries were multi-plied during the 1997-98 dry season (DS). Those in-cluded 243 incoming nursery nominations to 10INGER nurseries. Those will be included as testmaterials in the year 2000 INGER nurseries. In ad-dition, 27 blast monogenic lines were successfullymultiplied in the screenhouse.

Preparation of the 1999 INGER nurseries

Five ecosystem-based and four stress-orientedINGER nurseries were tested for viability and seedhealth and processed for dispatch in 1999.

Utilization of the 1997 INGER entries

The number of 1997 INGER entries used by partici-pating NARS for further yield evaluation and hy-bridization is given in Table 1.

A total of 219 entries from ecosystem-basednurseries and 108 from stress-oriented nurserieswere used as parents in the varietal improvementprograms of 14 countries. Breeding lines most fre-quently used in hybridization are listed in Table 2.

Some 412 entries were further evaluated in ad-vanced yield tests of NARS. Those included in fol-low-up yield trials in more than three countries aregiven in Table 3. Yield performance of IR62141-114-3-2-2-2, IR65610-105-2-5-2-2-2, and Qing LiuAi No. 1 was further assessed in advanced yield tri-als in six countries.

The International Rice Information SystemC.G. McLaren

Ambiguity in germplasm identification, difficulty intracing pedigree information, lack of integrationbetween genetic resources, and characterization,

Table 1. Utilization of 1997 INGER global nursery entriesby participating NARS.

Entries used (no.)Region and country

Yield testing Hybridization

East AsiaChina 16 42Korea - 9

Southeast AsiaCambodia 80 1Malaysia 10 4Myanmar 133 160Philippines 7 10Thailand 55 62Vietnam 57 51

South AsiaBangladesh 120 26Bhutan 16 -India 138 59Nepal 24 -Pakistan 44 29Sri Lanka 2 2

West Asia and North AfricaIran 23 14

Latin AmericaSurinam - 14

breeding, evaluation, and utilization data have beenidentified as major constraints to developing knowl-edge-intensive improvement programs in manycrops. The IRIS is a database system for the man-agement and integration of global information onrice genetic resources and crop improvement. IRISis part of a multicenter initiative known as the In-ternational Crop Information Systems (ICIS).

IRIS provides all rice researchers access to thelatest international information linked unambigu-ously to specific germplasm. IRIS allows scientiststo benefit from, and participate in, the developmentand deployment of new, knowledge-intensive cropimprovement systems that link information to theseeds being exchanged.

The Genealogy Management System

The core of the IRIS structure is a common genea-logical data model called the Genealogy Manage-ment System (GMS). The central idea of the modelis unique identification of germplasm and manage-ment of the homonyms and synonyms that arisenaturally in the process of germplasm developmentand utilization.


The GMS functions are:● Assign and maintain unique germplasm

identification.● Retain and manage information on genealogy.● Manage nomenclature and chronology of

germplasm development.The genealogical core links to various applica-

tions required by individual users. Some of the ap-plications will add genealogical data to the GMS,

while others will be analytical, displayinggenealogies or calculating coefficients of parentage,for example.

The Data Management System

The Data Management System (DMS) is the com-ponent of IRIS that manages environmental data,germplasm characterization, and evaluation data for

Table 2. INGER entries frequently used in 1997 as parents in NARS varietal improvement programs.

Designation Origin Frequency of use Countries where useda

Ecosystem-oriented nurseriesIR67017-13-3-3 IRRI 5 BGD, MYA, IND, IRNIR67039-115-3-1 IRRI 5 IND, IRN, MYA, VNMIR67423-42-2-3-3 IRRI 5 CHN, IND, IRN,MYA, SURIR65509-22-1-2-1R IRRI 4 CHN, IND, PAK, VNMIR66233-234-2-1-2 IRRI 4 CHN, IND, IRN, MYAIR65617-52-2-3-3-2-3 IRRI 4 BGD, PAK, PHL, THAIR65912-31-2-4-2-3-1 IRRI 4 BGD, MYA, PHL, THARP2095-5-8-31 India 3 BGD, PAK, THANanjing 63056 China 3 BGD, PAK, SURPusa Basmati 1 India 3 MYA, MYS, SURB6144 Indonesia 3 BGD, CHN, THAIR62141-114-3-2-2-2 IRRI 3 BGD, PAK, THAIR65610-105-2-5-2-2-2 IRRI 3 CHN, IND, PAKIR67423-53-2-3-3-2 IRRI 3 IRN, MYA, SURIR62127-55-1-2-2-3 IRRI 3 BGD, IND, THAStress-oriented nurseriesK479-2-3 India 4 MYA, IND, KORK39-96-1-1-1-2 India 3 MYA, IND, KORBaldo Italy 3 MYA, IND, KORIR-BB7 IRRI 3 CHN, MYS, VNMHexi 10 China 3 MYA, IND, KORYungen 9 China 3 MYA, INDK459-34-1-1-3 India 3 MYA, IND

aBGD = Bangladesh, CHN = China, IND = India, IRN = Iran, KOR = Korea, MYS = Malaysia, MYA = Myanmar, PAK = Pakistan, PHL = Philip-pines, THA = Thailand, SUR = Surinam, VNM = Vietnam.

Table 3. INGER entries frequently tested in NARS advanced yield trials, 1997.

Designation Origin Frequency of use NARSa

IR62141-114-3-2-2-2 IRRI 10 BGD, IND, MYS, PAK, THA, VNMQing Liu Ai No. 1 China 8 BGD, IND, MYS, PAK, THA, VNMB3632F-TB–1 Indonesia 7 BGD, CAM, NPL, PHL, THAIR65610-105-2-5-2-2-2 IRRI 7 BGD, CAM, IND, MYS, PAK, VNMB6149F-MR-7 Indonesia 6 BGD, CAM, NPL, PHL, THANanjing 63056 China 6 BGD, IND, PAKBG1639 Sri Lanka 6 BGD, IND, PAK, VNMIR63872-3-1-3-3-1 IRRI 6 BGD, IND, PAK, THA, VNMIR65617-52-2-3-3-2-3 IRRI 6 BGD, CAM, PAK, THA, VNMIR67423-42-2-3-3 IRRI 6 BGD, CAM, IND, IRN, MYA‘132’ Vietnam 6 BGD, IND, MYA, PAK, THA

aBGD = Bangladesh, CAM = Cambodia, CHN = China, IND = India, IRN = Iran, KOR = Korea, MYS = Malaysia, MYA = Myanmar, NPL = Nepal,PAK = Pakistan, PHL = Philippines, THA = Thailand, SUR = Surinam, VNM = Vietnam.


genetic resources and crop improvement projects.DMS links these data to genotype information in theGMS and to location information in the locationmanager as well as providing links to other special-ized data sources. DMS also allows integration ofdata from different studies, thus permitting a broadrange of queries across trials or types of factors andvariates.

The functions of the DMS are:● Store and manage documented and structured

data from genetic resources, variety evalua-tion, and crop improvement studies.

● Link data to specialized data sources such asGMS, location, and climate databases.

● Facilitate inquiries, searches, and data extrac-tion across studies according to structuredcriteria for data selection.

ICIS applications

ICIS applications are programs that access the data-base either for the purpose of installing or updatingthe database or for extracting and analyzing infor-mation in the database. They can be written by anyICIS user. As long as they only access the databasethrough the supplied access functions, they will beportable between different local installations andeven between different crop databases.

Current applications include data managementtools for installing ICIS databases, updating localdatabases to the central database, and launchinguser programs. Other applications allow users tobrowse the database and search for records, displaypedigrees, and calculate coefficients of parentage.The External Pedigree Input Tool allows the captureof germplasm and genetic resources information.The Set Generation Module allows breeders and

germplasm evaluation specialists to compose listsof crosses, selections or entries for development andevaluation while automatically updating the data-base and having immediate access to all informationknown about the germplasm.

Linkages

The ICIS structure allows databases such as IRIS tolink germplasm evaluation data to climate databasesand geographical information systems. IRIS alsolinks to SINGER and the USDA Germplasm Re-sources Information Network. Work is under way tospeed up these links via the Internet and to connectto Rice Genes and other international genomedatabases.

IRIS now permits scattered information gener-ated on rice germplasm to be integrated, linked tosources of seed, and put to work in plant improve-ment. Its distributed design allows all partners tohave access to the latest information and participatefully in the development of knowledge-intensivecrop improvement programs.

Seed health testing servicesT.W. Mew, S.D. Merca, C.C. Huelma,P.G. Gonzales, and J.O. Guevarra

The Seed Health Unit, under supervision of thePhilippine Plant Quarantine Service, processed 59incoming rice seed shipments with 16,065 seed lots(421.3 kg) during 1998 (Table 4). Their consign-ment is seen in Table 5. Among the quarantine ob-jects, weed seed contamination was only 0.8%,mainly due to Echinochloa spp. Insect-affected seedlots accounted for 4.7%, mainly due to Sitophilusoryzae and S. granarius. Blotter test of 556 incom-

Table 4. Origin of incoming seed shipments to IRRI, 1998.

Region Countries (no.) Shipments (no.) Seed lots (no.) Weight (kg)

East Asia 3 13 3,997 45.1Europe 2 4 29 .6Latin America 3 3 161 2.5Oceania 1 1 6 1.7South Asia 4 4 258 5.9Southeast Asia 8 22 10,982 344.8Sub-Saharan Africa 4 6 186 17.4West Asia and North Africa 3 6 446 3.3

Total 28 59 16,065 421.3


ing seed lots revealed that the brown spot fungi(Drechslera oryzae) affected 85% of the seed lots,followed by sheath rot (Sarocladium oryzae) 51%,bakanae (Fusarium moniliforme) 43%, leaf scald(Gerlachia oryzae) 20%, kernel smut (Tilletiabarclayana) 9%, and blast (Pyricularia oryzae) 8%.White tip (Aphelenchoides besseyi) affected 3% ofthe incoming seed samples. All the diseases, insects,and weeds found were collected and disposed of byautoclaving. All seed lots were subjected to post-entry seed treatments of hot water (HWT) at 52-57 oC for 15 min followed by fungicide slurry seedtreatment of benomyl and mancozeb both at 0.1%formulated product by seed weight.

A total of 376 phytosanitary certificates were is-sued in 1998 for outgoing shipments covering67,597 seed lots (1,963.4 kg) (Table 6). The bulk ofseed shipments to North America went to the Na-tional Seed Storage Laboratory, Fort Collins, Colo-

rado, for duplicate storage of the International RiceGenebank Collection.

Sources of outgoing seeds were INGER 27,996seed lots; PBGB 23,265 seed lots; IRG 15,886 seedlots; EPPD 400 seed lots; APPA 49 seed lots; andSWSD 1 seed lot. All outgoing seed lots werecleaned of quarantine objects. Routine seed healthtest of 1,475 outgoing seed lots revealed that S.oryzae affected 42% of the seed lots, followed byF. moniliforme 39%, G. oryzae 24%, T. barclayana4%, and P. oryzae 2%. A. besseyi were found in 2%of the outgoing seed lots.

Pre-export fumigation and HWT followed bybenomyl and mancozeb seed treatment, both at0.1% by seed weight, were administered on all out-going seeds except for countries that do not acceptfungicidal treatments.

Post-entry crop health inspection was done on4,747 entries in DS and 2,106 entry in WS. Themajor diseases observed were sheath rot affecting87% of the entries followed by sheath blight affect-ing 20% in DS. In WS, sheath rot affected 28% andsheath blight 2%. Fewer diseases were observed inWS, which could have been due to the El Niño (dry)weather phenomenon. None of the diseases ob-served during the initial seed multiplication wereintroduced by incoming entries.

A total of 9,718 entries were inspected for pre-export crop health data on materials of PBGB. InDS, the diseases were sheath rot affecting 2% ofentries and narrow brown leaf spot affecting 3%. InWS, narrow brown leaf spot affected 10% of theentries followed by bacterial leaf streak 5%, leafscald 4%, sheath rot 3%, and sheath blight 2%. Riceblast was only observed on 1% of the entries.

Table 5. Distribution of incoming rice seed shipments in1998.

Division Shipments Seed lots Weight(no.) (no.) (kg)

APPAa 4 364 38.9EPPb 3 235 1.6GRCc

INGERd 8 76 8.3IRGe 27 8,419 210.2PBGBf 17 6,971 162.3

Total 59 16,065 421.3

aAgronomy, Plant Physiology, and Agroecology. bEntomology andPlant Pathology. cGenetic Resources Center. dInternational Networkfor Genetic Evaluation of Rice. eInternational Rice Genebank. fPlantBreeding, Genetics, and Biochemistry

Table 6. Distributions of rice seed shipments with phytosanitary certification by Seed HealthUnit, IRRI, 1998.

Region Countries (no.) Shipments (no.) Seed lots (no.) Weight (kg)

East Asia 6 95 13,638 499.6Europe 11 42 533 24.9Latin America 8 16 4,038 105.6North America 2 25 14,695 18.4Oceania 3 14 2,384 22.1South Asia 6 85 15,164 595.6Southeast Asia 9 74 12,385 560.2Sub-Saharan Africa 7 9 1,250 41.5West Asia and North Africa 5 16 3,510 95.5

Total 57 376 67,597 1,963.4


Researchers from China (2), Myanmar (1), andBangladesh (1) were trained 1 Jul–20 Sep in riceseed health for crop management.

Program outlook

Germplasm conservation and the safe delivery ofgermplasm to researchers worldwide are importantand strategic components of IRRI’s researchagenda. Programmatic focus brings together the ac-tivities of the International Rice Genebank, INGER,and the Seed Health Unit and ensures that IRRI cancorrectly address those issues.

Our research on biosystematics contributes to themore efficient management of the wild species, and

facilitates utilization of this germplasm in rice im-provement. Policies for the on-farm conservation ofrice varieties will emerge from GRC’s research inthis strategic area, which has been given promi-nence in both the Convention on Biological Diver-sity and the FAO Global Plan of Action for the Con-servation and Sustainable Utilization of Plant Ge-netic Resources for Food and Agriculture.

Access to information on conserved germplasmand its use in breeding will be enhanced as we con-tinue to develop IRIS and ensure that the necessarystrategic links to IRGCIS, SINGER, and the devel-oping INGER information system are put in place.


Accelerating the impact of rice research

Strengthening partnership with NARS

East and Southeast Asia

CAMBODIA

Varietal improvementM. Sarom, O. Makara, P. Phon Hel, H. Yadana,and E. Javier

Farmer’s yields and acceptance of Cambodia-IRRI-Australia Project (CIAP)-released, improved local,long-duration rice varieties (CAR4, CAR5, andCAR6) were measured during 1995-98. The varie-ties performed well in wide-ranging environmentsand cultural practices. All exceeded the farmer’sbest variety in yield (Table 1) and acceptability.CAR4 was the most preferred variety, with an aver-age acceptance rate of 42%. The three varieties con-tribute significantly to higher production across40% of the rice-growing area of Cambodia.

Farming systems agronomyC. Phaloeun, T. Vuthy, S. Sakkhunthea, andH.J. Nesbitt

A technology package involving variety, landleveling, soil management, fertilizer, and integratedpest management (IPM) was tested during 1995-98in rainfed lowlands in southeastern Cambodia. Thetechnology increased rice yields by as much as140% and farmers’ income by 69%. However,farmers had to have off-farm income or ability toborrow money for investing in inputs to realize thefull potential of the technology package.

IRRI’s ability to make positive and lasting contribu-tions to poverty alleviation, food security, and sustain-able management of natural resources depends on● the quality and relevance of our research, and● the effective evaluation, adaptation, and delivery of

research products to users.New high-yielding rice varieties and knowledge-

based rice technologies can increase the productivityand efficiency of rice farming. The program, Accelerat-ing the Impact of Rice Research (IM), draws availableresearch results from the research programs, synthe-sizes them into usable technologies, and evaluatesand adapts them to specific rice-growing conditions incollaboration with national agricultural researchsystems (NARS). The IM program has four projects:● Strengthening partnership with NARS● Delivery of knowledge-intensive technologies (KIT):

Crop and Resource Management Network(CREMNET)

● Collecting, exchanging, and distributing knowledgeand information about rice

● Human capital development of NARS rice profes-sionals

Accelerating the impact of rice research 141

Crop protection and farming systems(socioeconomics)P.G. Cox, G.C. Jahn, Mak Solieng, Chhorn Nel,Tuy Samram, K. Bunnarith, and P. Chanthy

Farmer participatory research for rat management.CIAP researchers worked with Catholic ReliefServices during 1998 to identify weaknesses infarmers’ rat management practices and make im-provements in them. Farmers in nine villages al-ready used traps and baits, which were comple-mented by rat hunts. The work helped farmers un-derstand that destroying rats in their burrows in off-season improved control of rat populations.

Pest damage simulation. Four simulation trialsin a glasshouse determined the types and levels ofpest damage affecting rice yields at different cropstages. The results (Table 2) suggest that rice hasconsiderable capacity to compensate for or recoverfrom drastic damage at vegetative phase. Thus, itmay not be necessary to manage pests that restrict

their damage to leaves before panicle initiation (PI).Likewise, pests that cut tillers, such as rats, arelikely to reduce yields after PI. Cutting off 50% oftillers at stem elongation did not reduce yields ofIR66, which has the ability to grow new tillers, sug-gesting that IR66 could tolerate fairly heavy gallmidge damage before PI.

Integrated nutrient managementN. Heer, P. White, and M. Sana

The recently introduced Cambodian AgronomicSoil Classification System (CASC) provides a sim-ple means for agronomists and extension officers inCambodia to identify and manage soils. A surveyamong 22 agronomists and extension officers in 6provinces determined that CASC was used by all to

● identify the soil where their research trialswere located, and

● help farmers identify their soils and determineappropriate fertilizer rates.

Table 2. Yield response of IR66 to cutting off leaves and stems at different cropstages.

Mean yield (t ha-1)

Treatment Cutting Cutting Complete Completeoff leaves off 50% stem stem

(IR66) stems cutting cutting(IR66) (IR66) (CAR11)

Cut off all seedling leaves 3.1 2.8 0 1.2Cut off 50% of leaves at tillering 3.2 3.1 1.5 2.8Cut off 50% of leaves at booting 2.6 2.5 0.5 0.4Control 3.3 3.3 3.0 3.8

Table 1. Mean yield (t ha–1) of CAR4, CAR5, CAR6, and a local variety in on-farmadaptive trials in Cambodia, 1995-97.a

Variety 1995 1996 1997 Av

CAR4 2.8 ± 1.1 (23) 2.6 ± 1.0 (13) 3.1 ± 1.4 (15) 2.83± 1.2 (17)CAR5 2.7 ± 1.1 (17) 2.5 ± 0.9 (9) 3.0 ± 1.4 (11) 2.73± 1.1 (13)CAR6 2.8 ± 1.2 (23) 2.5 ± 0.9 (9) 3.1 ± 1.5 (15) 2.80± 1.2 (17)Local variety 2.3 ± 0.9 2.3 ± 0.9 2.7 ± 1.2 2.43± 1.0

a Number in parenthesis indicates the percentage yield advantage over the local variety.


Agricultural engineeringJ. Rickman, S. Bunna, and P. Sinath

Land leveling is used in Cambodia to improve wa-ter use efficiency and crop management in rainfedrice crops. Land leveling increased yields by morethan 30%. Good land preparation and water man-agement reduced weeding time from 21 to 5 d ha-1.Leveling also increased the opportunity for directseeding with 1 d ha-1 used, compared with 30 d ha-1

for transplanting. Water use efficiency was also im-proved by use of water from higher elevation fieldsto establish and improve crops in lower fields.

Yields in 1998 trials were compared in largefields (0.25–0.50 ha) with different degrees of lev-elness but with identical crop management and in-puts. A strong correlation was found between yieldand land levelness (Fig.1).

Animals, 2-wheel, and 4-wheel tractors havebeen successfully used to level fields with harrowsand leveling boards. These techniques required to-tal water coverage in the field. Four-wheel tractorswere effective in leveling both wet and dry fields.The cost of land leveling with a tractor ranged from$3 to $5 per centimeter of soil moved per hectare.Contractors are presently charging double thatamount. If appropriate plowing techniques areadopted, re-leveling should not be necessary for atleast 8-10 yr.

CHINA

S. Tang and NARS staff

The International Rice Molecular Breeding Pro-gram was organized and will be initiated in 1999.Collaboration on hybrid rice will continue. Seeds of261 Chinese rice varieties were sent to IRRI for re-search purposes.

INDONESIA

M. Syam and NARS staff

A rice crop intensification program involving thegrowing of a third crop of rice annually waslaunched in 1998. About 120,000 ha of irrigatedlowland areas in five provinces of Java and Baliwere covered. About 90% of the area had been har-vested by Dec 1998 with an average yield of 5.3 tha-1. Field observations in Bali were that three IRRI

lines (IR69075-1-1-3-2-11, IR69726-116-1-3, andIR71031-4-5-5-1) were highly resistant to tungrowhile IR64 was almost completely damaged by thedisease.

LAO PDR

J. Schiller, B. Linquist, K. Fahrney, and NARSstaff

The Swiss Agency for Development and Coopera-tion (SDC)-funded Lao-IRRI project started in Aug1990 and is currently in its third phase. In Nov 1998,the SDC indicated in-principle support for a Phase4 that will extend the project to Dec 2002.

Varietal improvement. By 1998, eight im-proved glutinous varieties had been released, five ofwhich had IRRI genotypes in their parentage.

Plant nutrition. Four varieties and N rates from0 to 120 kg ha-1 were compared in field trials in1998 dry season (DS). Combined analyses acrosssites indicated significant variety and N effects, andvariety × site interactions. The yield response to Nwas typically linear between 0 and 120 kg ha-1 forall varieties. Similar observations were made inrainfed lowland trials in wet season (WS).

The response of TDK1 to N in WS rainfed low-land trials was evaluated at 20 sites between 1993and 1998. Average yield without N was 0.3 t ha-1,lower in the southern and central Lao regions thanin the north. In the south and central regions, theaverage yield response of TDK1 was linear between0 and 90 kg N ha-1 (Fig. 2). In the north, yields didnot increase with N rates above 60 kg N ha-1. Lowersolar radiation may contribute to the lower yield inthe north.

1. Crop yield as affected by land levelness. CIAP, 1998.

10 2 3 4 5 6 70

1

2

3

4


Land levelness (SD in cm)

y=-278.63x + 3541.6

R2=0.66


Farming systems research. On-farm trials atrainfed lowland sites highlighted the potential forimproving yields by use of simple technology pack-ages based on use of improved varieties, fertilizermanagement, and agronomic practices. Averageyield of adopters of the full package was 56%higher (3.4 t ha-1) than partial adopters (2.3 t ha-1),and 108% higher than nonadopters (1.6 t ha-1) inChampassak Province. Average net return ofadopters of the full package was 43% greater ($510)than partial adopters ($356) and 96% higher thannonadopters ($259).

JAPAN

T. Morinaka, K. Marooka, and NARS staff

IRRI Hotline Vol.8 and News about Rice and Peo-ple were published in Japanese and copies of eachissue distributed to news media, policymakers, riceresearchers, and persons concerned in internationalcooperation. Selected articles of Hotline and Sci-ence on Line on the IRRI home page were alsotranslated into Japanese and distributed.

MYANMAR

A. Garcia and NARS staff

Split application of urea improved efficiency of ap-plied N. Results of 1997-98 DS experiments on ir-rigated rice were that gypsum (sulfur) application,combined with 4-6 split applications of urea N fer-

tilizer gave higher yields than the farmers’ practiceof applying half the recommended rate (28 kg Nha-1) during planting. Wet-season trials on uplandrice in Kalaw, Shan State, showed that locally pro-duced liquid BioSuper fertilizer partially substitutedfor N requirement.

A small credit scheme and community tree plant-ing were successfully organized to support farmers.Fifty-eight Myanmar Agricultural Services re-searchers and extension workers participated inthree in-country courses: Sustainability of the Com-munity-based Natural Resource Management (25),Field Collection and Preservation of RiceGermplasm (23), and Introduction to Basic Geo-graphic Information Systems (10).

South Asia

BANGLADESH

S. Bhuiyan and NARS staff

During the year, scientists from IRRI spent morethan 170 d working with scientists from the Bang-ladesh Rice Research Institute (BRRI) and otherorganizations on several collaborative projects.Those included yield gap research and the mega-project Poverty Elimination Through Rice ResearchAssistance (PETRRA), which will start in 1999.

INDIA

R.K. Singh and NARS staff

Initial results of research on farmers' participatorybreeding indicate that farmers’ and breeders’ selec-tion criteria based on agronomic traits did not differmuch. One of the early impacts of the project wasmanifested in terms of changing the mind-set ofbreeders. The interaction with farmers, as well associal scientists involved in the project, helpedbreeders to better appreciate the multiplicity offarmers’ goals and the complexity of the environ-ment.

East, Central, and Southern Africa (ECSA)M. Gaudreau, V. Balasubramanian, and NARSstaff

The inaugural Steering Committee Meeting ofECSA Rice Research Network (ECSARRN) washeld at Entebbe, Uganda. An ECSARRN project

2. Grain yield response of TDK1 in central and southern LaoPDR compared to northern Laos in rainfed lowland sites, 1993-98 WS.

0 20 40 60 80 1002.0

3.0

2.8

2.6

2.4

2.2

4.0

3.8

3.6

3.4

3.2


NorthSouth/Central

y=0,0153x + 2,404

R2=0.9967

y=0,0002x2 + 0.0263x+2.693

R2=0.9968

N rate (kg ha–1)


proposal was developed and submitted to the Asso-ciation for Strengthening Agricultural Research inEastern and Central Africa (ASARECA) for reviewand funding by potential donors.

MADAGASCAR

M. Gaudreau and NARS staff

Collaborative research programs. The UnitedStates Agency for International Development(USAID)-funded Madagascar-IRRI Environmentand Agriculture Research Project (US$1.5 M for 3yr) started in Jan 1998. A program to collect, char-acterize, and test the pathogenicity of a fungus thatattacks striga was established and trials on strigacontrol in upland rice were set up. An experimentto determine the fungi most effective against blackbeetle (Heteronychus) was established.

Latin America and the CaribbeanV. Balasubramanian and NARS staff

The annual and Technical Advisory Committeemeetings of the Caribbean Rice Industry Develop-ment Network (CRIDNet) and the annual meetingof the Caribbean Rice Association were held inHaiti in Feb 1998. IRRI provided limited researchsupport to CRIDNet through rice germplasm and in-formation exchange and provision of one chloro-phyll meter each to Guyana and Cuba.

Delivery of knowledge-intensivetechnologies: Crop and ResourceManagement Network (CREMNET)V. Balasubramanian, A.C. Morales, and NARSstaff

Rice production technologies are becoming morelocation-specific, complex, and knowledge-inten-sive with movement toward high yields (8-10 tha-1) in farmers’ fields. CREMNET is designed tofacilitate the identification, free exchange, partici-patory evaluation, and promotion of promisingtechnologies in rice farming.

Techniques for real-time N managementin rice

The nutritional status of rice plants reflects theavailability and uptake of nutrients from different

sources. Simple tools are available to monitor cropN status and to apply fertilizers at the right time tomeet crop demand.

CHLOROPHYLL METER

The chlorophyll meter, also called the SPAD meter,is a simple, portable diagnostic tool that monitorscrop N status in the field. When properly calibratedto locally important rice varieties and crop-growingconditions, the SPAD meter serves as an efficienttool for developing need-based, variable-rate N ap-plication on rice crops.

A SPAD threshold value of 35 works well forsemidwarf indica varieties in DS transplanted rice(TPR) systems in the Philippines. The value is re-duced to 32 for WS TPR when solar radiation islow. However, the SPAD threshold values for TPRhave to be kept at 35 for kharif (wet) season and 37-38 for rabi (dry) season in India to obtain highyields. This is probably due to higher solar radiationduring both seasons in India.

For wet-seeded rice (WSR) in the Philippines, aSPAD threshold of 29-30 is optimum for broadcastWSR with a planting density of 800 productive till-ers m-2, and 32 for row WSR with 650 productivetillers m-2. Thus, the critical SPAD value is in-versely related to plant density, which varies withcrop establishment methods.

We observed three outcomes with the use of theSPAD meter:

● An increase in grain yield but with a higherfertilizer N use. N use efficiency (NUE) wasthe same for both the farmers’ practice and theSPAD method, indicating efficient fertilizeruse by farmers. However, grain yield can befurther increased with additional Napplication, e.g., Nueva Ecija, Philippines,1996 DS (Table 3).

● A saving in N fertilizer use without reducingthe grain yield. Here the NUE is higher for theSPAD method than for the farmers’ practice,indicating the need for improving farmers’ Nmanagement practice, e.g., Nueva Ecija,Philippines, 1996 WS; Sukamandi, Indonesia,1996 DS (Table 3).

● An increase in grain yield and a reduction in Nfertilizer use. In this case, farmers’ NUE islow. Improvement in farmers’ fertilizer usepractice is needed to save N fertilizer and to


increase rice yields, e.g., New Cauvery Delta,India, 1996 DS; Cai Lay, Vietnam, 1996 WS(Table 3).

The cost of a SPAD meter is US$1,400, whichindividual farmers cannot afford. However, field re-searchers, extension soil specialists, crop consult-ants, and farmer cooperatives can purchase SPADmeters to monitor crop N status and advise farmerson N fertilization. CREMNET has distributed 38chlorophyll meters to various collaborators in Asiaand the Caribbean for evaluation and adaptation tolocal conditions. Use of the SPAD meter techniqueby NARS is increasing in Bangladesh, India, Indo-nesia, Myanmar, Philippines, and Vietnam.

LEAF COLOR CHART

Farmers generally use leaf color as a visual indica-tor of the rice crop’s need for N fertilizer. A Japa-nese prototype color chart was used by IRRI andPhilRice to develop an inexpensive leaf color chart(LCC) to determine the N fertilizer needs of ricecrops. The chart contains six gradients of greencolor from yellowish green (No. 1) to dark green

(No. 6). It is calibrated with the SPAD meter andused effectively for guiding N application in ricefields. A simple instruction sheet in the local lan-guage helps the farmer determine the correct timeof N application to rice crops.

Use of the LCC promotes timely and efficientuse of N fertilizer and can help minimize the pollu-tion of surface and groundwater. The chart can besuccessfully adapted and used in irrigated andfavorable rainfed rice ecosystems.

CREMNET will extend this technology to rice-growing countries of Asia, Africa, Latin America,and the Caribbean. Farmers in the Philippines andVietnam were eager to use the simple and handyLCC to manage N in their rice crops. The PhilippineDepartment of Agriculture distributed 15,000 colorcharts nationwide to agricultural extension agentsand farmer-cooperators. About 5,000 charts weredistributed to farmers in the Mekong Delta area ofVietnam. The Vietnamese farmers claim that adopt-ing the color chart saved them 20-25% of N ferti-lizer, avoided lodging, and increased grain yield inWSR (Table 4).

Table 3. Comparison of chlorophyll meter (SPAD) method with farmers’ practice for N management in rice in four coun-tries, 1996.

N used Increase or Grain Increase orSite and season Treatment (kg ha-1) decrease in yield decrease

N use (%) (t ha-1) in yield (%)

Nueva Ecija, Control 0 – 3.7 – Philippines Farmers’ practice 126 – 6.0 – 1996 DS SPAD 150 + 19 6.7 + 11

Nueva Ecija, Control 0 – 3.2 – Philippines Farmers' practice 101 – 4.2 – 1996 WS SPAD 73 – 28 4.2 + 0.1

Sukamandi, Control 0 – 4.8 – Indonesia Local recommendation 90 – 6.6 – 1996 DS SPAD 60 – 33 6.5 – 0.8

New Cauvery Control 0 – 5.3 – Delta, TN, Local recommendation 125 – 6.5 – India SPAD 60 – 52 7.1 + 10 1996 DS

Cai Lay, Control 0 – 2.8 – Vietnam Local recommendation 120 – 4.0 – 1996 WS SPAD 70 –42 4.0 + 2 WSR


Collecting, exchanging, and distributingknowledge and information about riceI. Wallace, G. Hettel, B. Hardy, S. Inciong, M.Movillon, and staff

IRRI is a major disseminator of rice research infor-mation. Activities include

● Creating, producing, and disseminatinginformation materials that cover rice researchand related issues, that create publicawareness, and that are accurate, interesting,and useful.

● Improving the publishing and disseminating ofIRRI research results and promoting globalexchanges of rice research information amongscientists.

● Making rice research information accessibleelectronically.

● Maintaining the IRRI Library andDocumentation Service as the world’s majorrepository of rice literature and facilitatingaccess to the collection by rice scientistsworldwide.

● Serving as a convener, clearinghouse, andforum for dialogue among IRRI partners andIRRI in setting program strategies and

priorities, planning rice research activities,sharing results, and promoting discussion oninstitutional and policy issues.

● Maintaining IRRI Riceworld as the world’sleading museum devoted to rice culture.

Public awareness and general publications

AUDIENCES AND KEY MESSAGES

The public awareness program is aimed at raisingglobal awareness of the importance of rice researchand IRRI research products. Activities focus on do-nors, policymakers, news media, NARS, advancedresearch institutions, nongovernment organizations(NGO), farmers’ organizations, and the generalpublic.

Many journalists visited IRRI in 1998. At least180 articles on rice and about IRRI were featured inleading publications in Sweden, Japan, Germany,Thailand, France, Hong Kong, Saudi Arabia, Re-public of Korea, Malaysia, Italy, Lao PDR, Viet-nam, United Kingdom, India, Bangladesh, USA,Myanmar, Australia, Canada, Indonesia, and thePhilippines. These articles resulted from the storyideas provided by IRRI.

Table 4. Comparison of leaf color chart (LCC) method with farmers’ practice for grain yield and N use efficiency in thePhilippines and Vietnam, 1996–98.

N used Increase or Grain Increase orSite and season Treatment (kg ha-1) decrease in yield decrease

N use (%) (t ha-1) in yield (%)

Nueva Ecija, Control 0 – 3.2 – Philippines Farmers' practice 101 – 4.2 – 1996 WS; LCC 48 – 52 4.2 + 0.4 17 farmers

Nueva Ecija, Control 0 – 3.5 – Philippines Farmers' practice 97 – 4.5 – 1997 WS; LCC 87 –10 4.3 4.4 12 farmers

Cai Lay, Farmers' practice 107 – 4.9 – Vietnam LCC 64 – 40 4.9 + 0.8 1996 summer; WSR; 14 farmers

Cai Lay, Farmers' practice 88 – 7.0 – Vietnam LCC (3 critical values) 64 – 27 7.1 + 1.4 1997-98 DS; WSR; 14 farmers


Six radio interviews were organized for IRRIstaff to describe the Institute’s major programs andkey research issues on two Philippine radio stations,BBC World Service Radio, Dutch National Radio,Australian Broadcasting Corporation, and the Sci-ence and Technology Report of the United States.National and foreign TV film groups visited IRRIto produce special segments or documentaries aboutrice and the Institute. Articles about IRRI were fea-tured on numerous worldwide web sites.

IRRI participated in four exhibitions—the Inter-national Cooperation Days in Japan (Oct), the Uni-versity of the Philippines Los Baños (UPLB) Loy-alty Day in the Philippines (Oct), the anniversary ofthe International Fund for Agricultural Develop-ment (IFAD) in Rome (Feb), and the FrankfurtBook Fair (Oct). The Institute gained special recog-nition from the Far Eastern Economic Review: win-ning a Silver Award for Asian Innovations.

COMMUNICATION MATERIALS

Five issues of the newsletter Hotline were producedin English and made available on the web. A corpo-rate report, IRRI 1997-1998: Biodiversity: Main-taining the Balance, was published and distributed.

New editions of Facts about Cooperation (FAC)for 25 donors and rice-producing countries werepublished. A Japanese version of the FAC bookletfor Japan was also published. A revised edition ofFacts about IRRI was produced. A Chinese versionof the IRRI slide show, Filling the World’s RiceBowl, was produced.

Scientific publishing

Nineteen titles were produced and distributed–10IRRI books, 7 IRRI discussion papers, a new publi-cations catalog, and the Program Report for 1997.A bibliography is provided in the section on publi-cations and seminars near the end of this programreport. Three of the IRRI books were dual imprintswith the Pacific Basin Study Center, the ThailandDevelopment Research Institute, and Kluwer Aca-demic Publishers. A significant set of papers on nu-trient use efficiency in rice cropping systems ap-peared in a special issue of Field Crops Research(Elsevier).

A complete revamping of the International RiceResearch Notes (IRRN) started in 1998 with the ap-

pointment of an editorial board of scientists. Thenew IRRN will debut in April 1999 with a new lookand features. IRRN has also been included inCornell University’s Essential Electronic Agricul-tural Library, which is a stand-alone compact disklibrary available only to scholars and students indeveloping countries. IRRN is also available on theInternet at http://www.cgiar.org/irri/irrn.htm.

IRRI’s efforts on the worldwide web resulted insignificant accomplishments. More than 50,000user sessions (more than 200,000 successful hits)were recorded on the IRRI homepage (http://www.cgiar.org/irri). It had electronic versions of theIRRN, the 1997 Program Report, Bt Gene Informa-tion Bulletin, Rolling MTP 1999-2001, Sandiwa(new monthly IRRI newsletter), and more than 200abstracts from 10 recent IRRI conferences andworkshops. The Riceworld site (http://www.riceworld.org) was redesigned and relaunched dur-ing International Centers' Week. The Riceweb site(http://www.riceweb.org) was recognized as a high-quality educational site by USA Today and DowJones, among others.

Successful credit card sales of IRRI books(through the German book vendor TRIOPS) beganon the Internet via the IRRI homepage. Orders formore than 100 books were received from around theworld.

Library and documentation service

IRRI Library continued providing scientific infor-mation about rice to scientists globally. An Exter-nal Program and Management Review panel notedthat “The Library is unparalleled in the world.”

COLLECTIONS

The Rice Bibliography grew by 5,480 references, ofwhich 66% were in English, 14% each in Chineseand Japanese, and the remaining 6% in other lan-guages. The online portion of the Rice Bibliographycovers literature from 1970 onward, more than172,000 references.

The online Library Catalog, containing mostlybook entries, grew to more than 33,000 biblio-graphic records, including 92 new dissertations onrice, from 10 different countries. The Library nowhas 1,370 active serial records and a growing col-lection of maps from many countries.


Table 5. International and regional conferences, workshops, symposia, and meetings hosted or cosponsored by IRRI in1998.

Date Title Venue Participants (no.) Countries (no.)

12-16 Jan Workshop on Quantification of Yield IRRI 29 7 Losses due to Rice Pests and Analysis of Survey Data in Plant Protection II

14-21 Jan Sysnet Workshop on Exploratory Land Philippines 51 3 Use Planning Methodology for Ilocos Norte Province, Philippines

19-22 Jan Planning and Implementation Workshop IRRI 26 5 for Crop Loss Assessment and Rice Straw Management Research

16-26 Feb Sysnet Workshop on Multiple Goal Land Vietnam 38 3 Use Planning for Can Tho Province, Vietnam

26-28 Feb Think Tank: Increasing the Impact of IRRI 20 9 Engineering in Agricultural and Rural Development

RELATIONS WITH NATIONAL AGRICULTURAL

RESEARCH SYSTEMS (NARS)

The Library received requests for information by e-mail, from countries as far away as Uruguay andMozambique. Most of these external correspond-ents had used the Library’s Web site and were fol-lowing up with specific queries.

Efforts were made to strengthen information tieswith NARS partners, most notably during extendedvisits to IRRI Library by librarians from Indonesia,Japan, and Pakistan. The IRRI librarian provided li-brary training in Bhutan and visited colleagues inIndonesia, Philippines, and Republic of Korea.

INFORMATION TECHNOLOGY

IRRI Library is fast becoming a library withoutwalls as outside electronic resources form an impor-tant part of the collection. Clients now have accessto a vast array of information that the IRRI Librarydoes not own in the traditional sense, and that is notlocated within the library building. Additional linksto electronic journals, newspapers, bookstores, li-braries, and reference sources were added duringthe year. Connections were expanded to the websites of partner institutes and organizations such asCAB International, the Food and Agriculture Or-ganization, and research centers within and outside

the Consultative Group on International Agricul-tural Research (CGIAR).

The Library provided web clients with a fre-quently revised list of forthcoming conferences ofinterest, often with electronic links to the organiz-ers. Ties were also established with an on-line pat-ent delivery service.

IRRI visitors, conferences, and workshops

IRRI welcomed about 71,000 visitors from 35 coun-tries during 1998. Many came to observe IRRI’sresearch activities and to explore the RiceworldMuseum and Learning Center. Visitors included 2heads of state, 13 state ministers, 10 ambassadorsand members of the diplomatic corps, 7 donor rep-resentatives, and 16 representatives of internationalorganizations. IRRI hosted or cosponsored 31 inter-national and regional conferences, workshops, sym-posia, meetings and reviews, in which 1,249 nation-als from 33 countries participated (Table 5).

Human capital development of NARS riceprofessionalsR. Raab and staff

IRRI, as a research and training institution, devel-ops human resources of NARS to improve their ca-pability for rice research. More than 12,000 degree


Table 5 continued.


24-25 Mar Annual Workshop of the IRRI-India India 26 1 Participatory Plant Breeding Project

23-30 Mar Land Use Systems Analysis Methodology India 41 3 for Haryana State, India

6-8 Apr Management of Rodent Pests in IRRI 23 8 Southeast Asia

20-22 Apr Prioritization of Rice Research in Asia IRRI 24 9

03-09 May Land Use Systems Analysis Methodology Malaysia 34 1 for Kedah-Perlis Region

11-13 May Inaugural Meeting of the Project “Deve- IRRI 21 9 lopment and Use of Hybrid Rice in Asia”

15-19 Jun SysNet International Workshop on Vietnam 180 9 Exchange of Methodologies in Land Use Planning

17-20 Jun Review and Planning Workshop for Thailand 39 10 Themes I and II of IPM Network

22-24 Jun Scaling Methodologies in Ecoregional Vietnam 57 11 Approaches for Natural Resource Management

29-31 Jul Workshop on Increasing Water Producti- IRRI 26 13 vity and Efficiency of Rice-based Cropping Systems

10-13 Aug First Technical Committee Meeting of IRRI 11 7 the Project “Development and Use of Hybrid Rice in Asia”

24-28 Aug IRRI-ACIAR Workshop on Strategic IRRI 32 11 Research on Gender Issues in Rice- based Household Economy

2-3 Sep Workshop on USAID-sponsored IRRI-US USA 29 3 University Collaboration

16 Sep Natural Resource Management in the Chao Thailand 105 6 Phraya Basin: an Ecoregional Approach

21-25 Sep Irrigated Rice Research Consortium/ People's 39 10 IPMNet/INMNet Joint Technical and Republic of Steering Committee Meetings China

21-25 Sep Upland Rice Research Steering and Thailand 72 11 Technical Committee Meetings

22-24 Sep Third IPM Network Steering China 16 9 Committee Meeting

6-8 Oct Steering Committee Meeting of the Project “Development and Use of Hybrid India 12 7 Rice in Asia”

12-15 Oct Nutrient Research in Rainfed Lowland Rice Thailand 75 14


Table 5 continued.


15 Oct Rainfed Lowland Rice Research Consortium Thailand 14 7 9th Steering Committee Meeting

20 Oct Ecoregional Approach for Planning and Myanmar 14 1 Management of Land and Other Natural Resources in the Ayerwaddy Delta

9-10 Nov Technical Workshop on Ecoregional Ap- Vietnam 42 4 proaches for Natural Resource Manage- ment in the Red Basin, Vietnam

9-11 Nov Workshop on Rice Tungro Management IRRI 45 8

16-20 Nov Center-Commissioned External Review IRRI 55 4 (CCER) of the Rainfed Lowland Rice Program

23-27 Nov Research Methods for Studying Weed IRRI 10 7 Succession

30 Nov-2 Dec Sysnet Technical Review Workshop Thailand 25 3

1-3 Dec Workshop on Genetic Improvement for IRRI 47 12 Rice in Water-limited Environments

Table 6. Participants in degree and postdegree training at IRRI, 1998.

PhD scholarsAlam, Muhammed Murshedul BangladeshBiswas, Jatish Chandra BangladeshChharom, Chin CambodiaOberthur, Thomas GermanyMuhsin, Muhammad IndonesiaAlinia-Gerdroudbari, Faramarz IranFallah, Allahyar IranNouanthasing, Lasay Lao PDRRamanantsoanirina, Alain Marie Justin MadagascarRazafinjara, Aime Lala MadagascarEow, Boon Tiak MalaysiaHtet, Kyu MyanmarHtut, U Tin MyanmarThet, Khin Maung MyanmarWinn, Tun MyanmarKhadka, Yajna Gajadhar NepalAbbasi, Fida Mohammad PakistanArif, Muhammad PakistanAsghar, Muhammad PakistanFaiz, Faiz Ahmad PakistanHussain, Fayyaz PakistanIjaz, Muhammad PakistanRillon Jr., Guillermo S. PhilippinesTado, Caesar Joventino M. PhilippinesTrillana, Nemesio U. PhilippinesDirie, Ahmed Mohamoud SomaliaLersupavithnapa, Boontium ThailandCuong, Ngo Luc VietnamNgo, Ngoc Hung VietnamNguyen, Van Hong Vietnam

Tran, Chi Thien VietnamTruong Van, Tuyen VietnamCui, Kehui ChinaFu, Binying ChinaJianli, Wu ChinaLi, Luping ChinaLu, Wenjing ChinaTu, Jumin ChinaYahai, Lu ChinaYueqiu, He ChinaZhong, Daibin ChinaZhong, Xiaoyan ChinaZhong, Xuhua ChinaZiqi, Wang ChinaBaisakh, Niranjan IndiaDey, Moul IndiaKaur, Jatinder IndiaMathan, Natarajan IndiaMitra, Sudip IndiaNath, Palash Deb IndiaEsfahany, Masoud IranNaoyoshi, Kawano JapanOkada, Kanako JapanOjha, Gana Pati NepalBernardo, Eleuterio Noel PhilippinesNghia, La Tuan VietnamDeka, Nivedita IndiaLourdusamy, Gabriel Stephen IndiaAbdullah, Buang IndonesiaBhandari, Hum Nath Nepal


Trolove, Stephen Neil New ZealandBorines, Lucia PhilippinesCabuslay, Gloria PhilippinesDe Los Reyes, Jeannelyn PhilippinesLumbo, Susanita PhilippinesLinwattana, Grisana ThailandSripongpankul, Krishnapong ThailandGraw, Stephen United StatesLe, Cam Loan VietnamLe, Thi Phuong VietnamTran, Thi Ut Vietnam

MS scholarsSattari, Majid IranInthavong, Soulaphone Lao PDRRasabandit, Sengpaseuth Lao PDRAndriantsimialona, Dodelys MadagascarRakotomalala, R. Mbolarinosy MadagascarAdhikari, Chiranjibi NepalUpadhyay, Bhawana NepalAbao, Jr., Elias B. PhilippinesOng, Marilyn A. PhilippinesPhengchanh Somphet Lao PDRLe Van, Lang VietnamNgo, Dang Phong VietnamNguyen, Thi Phong Lan VietnamThach, Thi Ngoc Anh VietnamTruong, Thi Ngoc Chi VietnamShimizu, Akifumi JapanVarghese, Pulickal IndiaBhattarai, Kiran NepalAlcantara, Jovencio PhilippinesMadamba, Reina Suzette PhilippinesMaghirang, Reycel DM PhilippinesUlat, Victor Jun Philippines

Table 6 continued.

Nondegree on-the-job traineesDema, Kezang BhutanGolinowski, Shawn Paul CanadaRichards, Barbara CanadaSchnupf, Mirjam CanadaGao, Lizhi ChinaHu, Fengyi ChinaMa, Zhenrong ChinaWang, Ying ChinaXie, Xiaobo ChinaKurniawan, Hakim IndonesiaMinantyorini IndonesiaSetyowati, Mamik IndonesiaAdachi, Shimpei JapanJeong, Eung-Gi KoreaLakmaitry, Khamsone Lao PDRAbro, Abdul Haque PakistanAskari, Ejaz PakistanBhand, Amir Ali PakistanOad, Gulshan Lal PakistanShah, Zahoor Hussain PakistanNewingham, Ma. Cristina V. PhilippinesBarnard, Katherine Patricia United KingdomAnh, Ta Hoang VietnamDo Tuan, Khiem VietnamMai, Duong Thi Hong VietnamMinh, Vo Quang VietnamNguyen, Thach Can VietnamNguyen, Van Tao VietnamTran, Danh Suu Vietnam

InternsManio, Denise AustraliaChung, Carrie-Lee CanadaGolinowski, Shawn Paul CanadaGray-Donald, James Canada

scholarships, postdegree on-the-job training, andshort-term group training fellowships have beenprovided to NARS scientists since 1961.

Degree and postdegree training

Degree and postdegree training provides rice scien-tists with opportunities to pursue a PhD or MS de-gree or acquire relevant skills through an on-the-jobtraining or an internship with IRRI scientists. In1998, IRRI extended degree and postdegree train-ing opportunities to 126 scientists, mainly from theAsian region (Table 6). Fifty-six scholars and fel-lows completed their programs in 1998 (Table 7).

Development of short-term courses

Short-term group courses provide NARS scientistswith an opportunity to update their knowledge and

skills on specific areas of rice science. Eleven groupcourses in 1998 attracted 144 NARS scientists from18 countries.

Genetic Evaluation and Utilization (GEU) train-ing at Ubon, Thailand, focused on the rainfed eco-system. An IRRI plant breeder was the course coor-dinator.

Development of new training methodology

IRRI intensified efforts to improve its capability fordistance education during the year. Implementationof an International Development Research Centre-funded project, Application of Distance LearningTechnologies to Human Capital Development inNARS, was initiated. IRRI, Simon Fraser Univer-sity, and the Commonwealth of Learning collabo-rate in this project. IRRI staff members conductedan assessment of connectivity capabilities and re-


quirements of a recipient site in Hyderabad, India.Preparations continued for the first IRRI onlinecourse on Experimental Design and Data Analysis(EDDA) in collaboration with Simon Fraser Uni-versity. The whole course will be ready for pre-test-ing by summer 1999.

TRAINING MATERIALS DEVELOPMENT

IRRI develops training materials for use by bothtrainers and trainees in group courses. Training ma-terials were produced for courses on

● GEU for rainfed lowland rice ecosystems● Instructional video production (supplementary

readings)

● Integrated pest management (IPM)(1st ed.)● Rice tungro disease identification and

management (one for extension officers, onefor farmers)

● Problem-based technology generation forrainfed lowland environments-Indonesiaoffering

Collaborative in-country training

Collaborative in-country courses were initiated in1989 to help develop NARS institutions’ indig-enous training capability and to complement IRRItraining activities at headquarters. Fifteen collabo-rative in-country courses were offered in 1998,training 257 NARS scientists (Table 8).

Table 7. Scholars and trainees who completed training at IRRI during 1998.a

Type I Type II Type IIICountry Total

PhD MS PhD MS ND

AfricaMadagascar 0 0 0 1 0 1Somalia 0 0 1 0 0 1

Subtotal 0 0 1 1 0 2

AsiaBangladesh 0 0 1 0 0 1Bhutan 0 0 0 0 1 1Cambodia 0 0 1 0 0 1China 3 0 0 0 5 8Indonesia 0 0 0 0 3 3Iran 0 0 1 0 0 1Japan 0 1 0 0 0 1Korea 0 0 0 0 1 1Lao PDR 0 0 1 1 1 3Malaysia 0 0 1 0 0 1Nepal 0 0 1 1 0 2Pakistan 0 0 2 0 5 7Philippines 1 1 4 2 1 9Thailand 0 0 0 1 0 1Vietnam 0 0 0 2 7 9

Subtotal 4 2 12 7 24 49

EuropeGermany 0 0 1 0 0 1United Kingdom 0 0 0 0 1 1

Subtotal 0 0 1 0 1 2

North AmericaCanada 0 0 0 0 3 3

Subtotal 0 0 0 0 3 3Total 4 2 14 8 28 56

aType 1 = MS and PhD scholars, thesis research at IRRI; Type II = MS and PhD scholars, coursework and thesis at IRRI; Type III = on-the-jobor nondegree training.


Table 8. Participants in collaborative group training courses. IRRI, 1998.

Course and date Participants (no.)/country

EDDA/IRRISTAT in Chlorophyll Meter 16 Indonesiaand Leaf Color Chart Technology28 Sep-3 Oct

IRRISTAT Training 6 Thailand14-16 Oct

IRRISTAT Training 10 Lao PDR19-21 Oct

Introduction to GIS Training Course 9 Myanmar19-30 Oct

Experimental Design and Data 8 BangladeshAnalysis with IRRISTAT22-30 Oct

Presentation Skills Course for Lao 17 Lao PDRTrainers and Scientists26 Oct-6 Nov

Training on Data Management and 17 IndiaDocumentation for Genetic Resources26 Oct-7 Nov

Refresher Course on Identification 17 Philippinesand Management of Rice TungroDisease for DA Technicians27 Oct

Rice Tungro Disease Identification28 Oct 38 Philippines29 Oct 35 Philippines

Subtotal 215 Total 257

Course and date Participants (no.)/country

RegionalIntegrated Pest Management Host: Philippines17 Aug-9 Oct 3 Cambodia

2 Lao PDR2 Philippines1 Colombia1 Madagascar

Rice Production Research Host: Thailand(Course 6) 8 Cambodia6 Oct-27 Nov 1 Ghana

3 Lao PDR1 Surinam2 Tanzania2 Thailand

Subtotal 26

Consortium or NetworkProblem-based Technology Genera- 16 Indonesiation for Rainfed Lowland Environments9-22 Apr

Subtotal 16

NationalTransformation and Molecular 10 IranAnalysis of Transgenic Plants17-27 Aug

Field Collection and Conservation 27 Myanmarof Rice Germplasm, 14-19 Sep

IRRISTAT Training 5 Cambodia16 Sep

Regional in-country courses are conducted col-laboratively with a NARS institution for an interna-tional group of trainees. Two regional courses wereconducted for 26 trainees from 9 countries in Asiaand Africa—IPM by the National Crop ProtectionCenter of the University of the Philippines LosBaños and Rice Production Research course by thePathum Thani Rice Research Institute in Thailand.

National in-country courses are adapted to thespecific needs of the requesting country. Twelve na-tional courses were conducted in 9 countries, up-grading the skills of 142 rice scientists. Moreover, afarmer’s version of one of the courses (Rice TungroDisease Identification and Management) trained 73farmers.

Network and consortium courses are requestedand funded by research networks and consortia. Thecourse on Problem-based Technology Generationfor Rainfed Lowland Environments conducted in

Bogor and Pati, Indonesia, for the Rainfed LowlandRice Research Consortium.

IRRI also assists national systems in formulatingtheir own training programs. Training needs assess-ments were made and training plans were developedfor Cambodia and Papua New Guinea.

Program outlook

The Strengthening Partnership with NARS projectwill continue to support country and regional col-laborative projects for strengthening NARS capa-bilities and collaborative research. The IRRI liaisonoffices in different countries will help develop newprojects and identify funding sources; monitorprogress of all collaborative research activities; fa-cilitate in-country training, workshops and confer-ences, and visits of scientists; and assist in the ex-change of information and knowledge among rice


scientists. IRRI-NARS research dialogues and plan-ning meetings will be held in India, Indonesia, Ne-pal, Philippines, and Sri Lanka in 1999.

CREMNET will continue to evaluate the chloro-phyll (SPAD) meter, LCC, controlled-release urea,and urea briquette deep placement in four countries.Farmers will be surveyed to gain increased under-standing of their knowledge and rationale in ferti-lizer use on rice in Bangladesh and India.

Information and knowledge exchange activitieswill continue and ways and means of efficiently dis-seminating information about rice and IRRI will bedeveloped. Web activities will assume even greaterimportance as IRRI sites are redesigned to makethem more attractive and easier to search, whilemore content is added from IRRI programs, centers,and divisions. Web-based sale of IRRI publicationswill likely increase as customers become aware of acredit card option as part of a shopping basket con-cept.

IRRI will publish around 20 titles in 1999 and In-ternational Rice Research Notes (IRRN) will ex-pand its content under a new editor-in-chief and edi-torial board.

The Riceworld Museum will unveil as many asnine new exhibits, including displays on the CGIARand IRRI-NARS collaboration, as well as a re-vamped look at some IRRI milestones of the pastfour decades.

A complete overhaul of library acquisitions isplanned with new staff and computer software ex-pected early in 1999. In addition, the Library willextend its activities into Lao PDR, sign an informa-tion memorandum of understanding with partners inKorea, and add new online services such asFirstSearch, which provides access to more than 60databases and document delivery suppliers.

IRRI will maintain about 85 scientists in its de-gree and postdegree training programs. About 30scientists should complete their studies by the endof 1999.

Fourteen regular and three regional courses for amaximum of 200 scientists are planned. Newcourses will be designed and developed during1999: 1) Modern Rice Farming and 2) TransgenicRice: Production and Deployment with Special Ref-erence to Sheath Blight and Rice Stem Borer Resist-ance.

Collaborative in-country courses for 1999 willinclude Problem-based Technology Generation forRice Environments in collaboration with CIAP forrice scientists in Cambodia; Engineering for RiceAgriculture in Bangladesh; Scientific Writing andPresentation and Community-based Natural Re-source Management (CBNRM) in Bhutan; StrategicPlanning for Effective GO-NGO Collaboration insupport of an ongoing project in northeast Thailand;and CBNRM in Myanmar in collaboration with theSoutheast Asian Regional Center for GraduateStudy and Research in Agriculture (SEARCA).

IRRI will improve its training strategy throughan in-depth review during 1999 and will seek direc-tion for its distance education initiatives through ameeting of distance and open learning experts. Staffskills on training in the distance mode will be im-proved through training and teamwork with infor-mation and communication technology profession-als.

Collaboration with universities and other train-ing institutions will be explored and used to retoolIRRI staff to enhance quality of training for NARSscientists.


Affiliations of collaborating researchers1Research Institute for Rice, Indonesia.2Philippine Rice Research Institute, Philippines.3Zhejiang Agricultural University, China.4Soil and Water Management Research Institute, India.5Pathum Thani Rice Research Center, Thailand.6National Institute for Soils and Fertilizers, Vietnam.7Cuu Long Delta Rice Research Institute, Vietnam.8Vietnam Agricultural Science Institute, Vietnam.9Malaysian Agricultural Research and Development Institute, Malaysia.10Department of Agriculture, Thailand.11Narendra Deva University of Agriculture and Technology, India.12Orissa University of Agriculture and Technology, India.13Ubon Rice Research Center, Thailand.14Texas Tech University, USA.15Nagoya University, Japan.16University of Adelaide, Australia.17Cornell University, USA.18International Food Policy Research Institute, USA.19Hokkaido University, Japan.20National Agriculture Research Center, Japan.21Shikoku National Agricultural Experiment Station, Japan.22Oklahoma State University, USA.23North Carolina State University, USA.24Texas A&M University, USA.25University of Maryland, USA.26Institut national de la recherche agronomique, France.27National Institute of Agrobiological Resources, Japan.28Agricultural Genetics Institute, Vietnam.29Harvard Medical School, USA.30Massachusetts General Hospital, USA.31Indira Gandhi Agricultural University, India.32Guangdong Academy of Agricultural Sciences, China.33West Africa Rice Development Association, Cotê d'Ivoire.34Hokuriku National Agricultural Experimental Station, Japan.35Centre for Cellular Molecular Biology, India.36Rice Research Institute, Iran.37Institute of Plant Sciences, The Swiss Federal Institute of Technology, Switzerland.38University of Tokyo, Japan.39University of Hanover, Germany.40Thai Nguyen University, Vietnam.41Katholieke Universiteit Leuven, Belgium.

Affiliations of collaborating researchers 155

Publications and seminars 163

Publications and seminars

Institute publications

BooksAllelopathy in rice. 1998. 154 p.IRRI 1997-1998. Biodiversity—maintaining the

balance. 1998. 58 p.Pest management of rice farmers in Asia. 1998.

245 p.Rainfed lowland rice: advances in nutrient

management research. 1998. 304 p.Sustainability of rice in the global food system.

1998. 404 p.Program report for 1997. 1998. 176 p.Impact of rice research. 1998. 428 p.Advances in hybrid rice technology. 1998. 443 p.

Periodicals/serialsInternational rice research notes, vol. 23, nos. 1-3.IRRI discussion paper series., nos. 23-36.

Agricultural Engineering

Bell MA, Douthwaite B, de Padua D, Rickman JF.1998. Rising to the challenge: increasing theimpact of engineering in Asia. In:Proceedings of the International AgriculturalEngineering Conference. Bangkok(Thailand): Asian Institute of Technology. p1012-1018.

Bell MA, Rickman JF, Castro EC Jr., Aclan LB,McNamara J. 1998. Precision land levelingfor rice production in Asia. In: Proceedings ofthe International Agricultural EngineeringConference. Bangkok (Thailand): AsianInstitute of Technology. p 257-264.

Borlagdan PC, Douthwaite B, Alihamsyah T, BellMA. 1998. Rainfed lowland rice cropestablishment in Central Java: practices,problems, and opportunities. In: Hsiu-YingLu, Jih-Min Sung, Ching Huei Kao, editors.Proceedings of the 3rd Asian Crop ScienceConference. Taichung (Taiwan): The ChineseSociety of Agronomy.

Agronomy, Plant Physiology, andAgroecology

Auld BA, Watson AK, Mabbayad MO, Ciotola M,Hetherington SD. 1998. Biocontrol of weedswith fungi in developing nations: the role ofbioherbicides. Abstracts. Biological control ofweeds workshop. 7th International Congress ofPlant Pathology, Edinburgh, UK.

Banoc DM, Yamauchi A, Kamoshita A, Wade LJ.1998. Genotypic variation in developmentalplasticity of rice seminal root system under thecomplex anaerobic-aerobic soil watertransitions. Jpn. J. Crop Sci. 67: 422-423.

Bronson KF, Cassman KG, Wassmann R, Olk DC,van Noordwijk M, Garrity D. 1998. See Soil andWater Sciences.

Cassman KG, Peng S, Olk DC, Ladha JK,Reichardt W, Dobermann A, Singh U. 1998.Opportunities for increased nitrogen-useefficiency from improved resourcemanagement in irrigated rice systems. FieldCrops Res. 56:7-39.

Castella JC, Husson O, Le Quoc Doanh, Ha DinhTuan. 1998. Implementing the ecoregionalapproach in the Red River Basin uplands


(Vietnam): the Mountain AgriculturalSystems (SAM) Project. In: Proceedings ofthe Ecoregional Planning Workshop for theRed River Basin, Vietnam, 6-8 Oct 1997,Ministry of Agriculture and RuralDevelopment, Hanoi, Vietnam.

Centeno HGS, Sheehy JE. 1997. Simulatingpotential rice yield at different environments.A case study. In: Manton M, Phelon A, VirjiH, editors. Proceedings of the Workshop onClimate Variability, Agricultural Productivity,and Food Security in the Asian MonsoonRegion, Bogor, Indonesia. Report No. 2.p 29-34.

Centeno HGS, Hammer GL, Sheehy JE, Stone R.1998. The impacts of ENSO on riceproduction in the Asia-Pacific region. In:Proceedings of the 23rd Conference of Forestand Agriculture Meteorology, New Mexico,USA.

Centeno HGS, Hammer GL, Sheehy JE, Stone R.1998. The impacts of ENSO on riceproduction in Central Luzon. In: Proceedingsof the Annual Scientific Meeting, Federationof Crop Science Societies of the Philippines,Cebu City, Philippines.

De Luna LZ, Watson AK, Paulitz TC. 1998.Infection structures of Curvularia tuberculataand C. oryzae on Cyperaceae weeds.Phytopathology 88:S135.

Dobermann A, Cassman KG, Mamaril CP, SheehyJE. 1998. see Soil and Water Sciences.

Edmeades GO, Bolanos J, Banziger M, RibautJ-M, White JW, Reynolds MP, Lafitte HR.1998. Improving crop yields under waterdeficits in the tropics. In: Chopra VL, SinghRB, Varma A, editors. Crop productivity andsustainability—shaping the future.Proceedings of the 2nd International CropScience Congress. New Delhi: Oxford andIBH. p 437-451.

Fukai S, Kwon YW, Sinclair TR, Wade LJ. 1998.Suggestions for potential authors from editors.Plant Prod. Sci. 1: 300.

George T. 1998. Nutrient decision-aids for thetransition to high value production systems inerosion-free Asian uplands. In: Proceedingsof the. 16th World Congress of Soil Science,20-26 Aug 1998. Montpellier (France):CIRAD.[in CD-ROM]

Henderson S, von Caemmerer S, Farquhar GD,Wade LJ, Hammer GL. 1998. Correlation ofcarbon isotope discrimination and transpirationefficiency in genotypes of C

4 Sorghum bicolor

in glasshouse and field. Aust. J. Plant Physiol.25: 111-123.

Ito O. 1998. Strategy for rice production technolo-gies at IRRI. In: Sustainable agricultural devel-opment compatible with environmental con-servation in Asia. Japan: Japan InternationalResearch Center for Agricultural Sciences.p191-202.

Kamoshita A, Fukai S, Muchow RC, Cooper M.1998. Genotypic variation for grain yield andgrain nitrogen concentration among sorghumhybrids under different levels of nitrogenfertiliser and water supply. Aust. J. Agric.Res. 49:737-747.

Kamoshita A, Fukai S, Muchow RC, Cooper M.1998. Physiological processes determininggenotypic variation for grain yield and grainnitrogen concentration among sorghumhybrids under different nitrogen fertiliserconditions. I. Hybrids with similar phenology.Aust. J. Agric. Res. 49:1267-1276.

Kamoshita A, Fukai S, Muchow RC, Cooper M.1998. Physiological processes determininggenotypic variation for grain yield and grainnitrogen concentration among sorghumhybrids under different nitrogen fertiliserconditions. II. Hybrids with contrastingphenology. Aust. J. Agric. Res. 49:1277-1286.

Katayama K, Ito O, Rao TP. 1998. Seedling charac-teristics and retention of current photosynthatesin leaves in relation to initial growth in pigeonpea (Cajanus cajan L. Millsp.) and cowpea(Vigna sinensis Endl.). Soil Sci. Plant Nutr.44(3):477-480.

Khush GS, Peng S, Virmani SS. 1998. see PlantBreeding, Genetics, and Biochemistry.

Kiniry JR, Landivar JA, Witt M, Gerik TJ, CalveroJ, Wade LJ. 1998. Radiation-use efficiencyresponse to vapour-pressure deficit for maizeand sorghum. Field Crops Res. 56: 265-270.

Ladha JK, Kirk GJD, Bennett J, Peng S, ReddyCK, Reddy PM, Singh U. 1998. see Soil andWater Sciences.


Lafitte HR. 1998. Research opportunities toimprove nutrient-use efficiency in ricecropping systems. Field Crops Res. 56:223-236.

Latore J, Gould P, Mortimer AM. 1998 The spatialdynamics and critical patch size of annual plantpopulations. J. Theor. Biol. 190:277-285.

Masangkay RF, Mabbayad MO, Paulitz TC,Watson. AK. 1998. Host range of Alternariaalternata f. sp. sphenocleae causing leafblight of Sphenoclea zeylanica. Can. J. Bot.(in press)

Mortimer AM. 1998. The need for studies on weedecology to improve weed management. In:Labrada R, editor. Expert consultation on weedecology and management. Rome: Food andAgriculture Organization. p 15-22.

Mortimer AM. 1998. Weed management andfarmer decision making—the role ofecological studies. In : Ali Abdul Hamid,Lum Keng Yeang, Tosiah Sadi, editors.Integrating science and people in rice pestmanagement. Kuala Lumpur: MalaysianAgricultural Research and DevelopmentInstitute. p 117-126.

Olk DC, Cassman KG, Mahieu N, Randall EW.1998. Conserved chemical properties ofyoung humic acid fractions in tropicallowland soil under intensive irrigated ricecropping. Eur. J. Soil Sci. 49:337-349.

Olofsdotter M. 1998. Allelopathy for weed controlin organic farming. In: El Bassam N,. Behl RK,Prochnow B, editors. Sustainable agriculturefor food, energy and industry—strategiestowards achievement. London: James & JamesScience Publisher. p 453-465.

Peng S, Cassman KG. 1998. Upper thresholds ofnitrogen uptake rates and associated nitrogenfertilizer efficiencies in irrigated rice. Agron.J. 90:178-185.

Peng S, Laza RC, Khush GS, Sanico AL, VisperasRM, Garcia FV. 1998. Transpiration effi-ciencies of indica and improved tropicaljaponica rice grown under irrigated condi-tions. Euphytica 103:103-108.

Ram S, Chauhan RPS, Singh BB, Singh VP. 1998.Response of wet season rice (Oryza sativa) tonitrogen and phosphorus in partially re-claimed sodic soil. Indian J. Agric. Sci.67(11): 514-517.

Rao TP, Ito O. 1998. Differences in root systemmorphology and root respiration in relation tonitrogen uptake among six crop species. JARQ32(2): 97-103.

Raybould AF, Mortimer AM, Bullock JM, Gray AJ.1998. Stress tolerance and weediness.Wareham, Dorset (UK): Institute of TerrestrialEcology. 162 p.

Sanetra CM, Ito O, Virmani S, Vlek PLG. 1998.Remobilization of nitrogen from senescingleaves of pigeon pea (Cajanus cajan (L.)Millsp.): genotypic differences across maturitygroups? J. Exp. Bot. 49(322): 853-862.

Sheehy JE, Dionora MJA, Mitchell PL, Peng S,Cassman KG, Lemaire G, Williams RL. 1998.Critical nitrogen concentrations: implicationsfor high-yielding rice (Oryza sativa L.)cultivars in the tropics. Field Crops Res. 59:31-41.

Sheehy JE, Mitchell PL, Beerling DJ, TsukaguchiT, Woodward FI. 1998. Temperature of ricespikelets. Thermal damage and the concept ofa thermal burden. Agronomie 18: 449-460.

Singh G, Singh VP, Singh OP, Singh RK. 1998.Production potential of various croppingsystems in flood-prone areas of Uttar Pradesh.Indian J. Agron. 42 (1): 9-12.

Singh U, Ladha JK, Castillo EG, Punzalan G,Tirol-Padre A, Dequeza M. 1998. Genotypicvariation in nitrogen use efficiency inmedium- and long-duration rice. Field CropsRes. 58: 35-53.

Singh VP, Sovyanhadi Y. 1998. Kinetics ofphosphate fixation in acid sulfate, iron-toxicand neutral soils. Oryza 35(2): 95-105.

Srivastava PC, Gangwar MS, Singh VP. 1998.Adsorption-desorption of Zn in Mollisols andtheir relationship with the uptake of fertilizerapplied zinc by rice. Commun. Soil Sci. PlantAnal. 30: 3-4.

Turkelboom F, Trébuil G. 1998. A multiscaleapproach for on-farm erosion research:application to northern Thailand highlands.In: Penning de Vries FWT, Fahmuddin A,Kerr J, editors. Soil erosion at multiple scales:principles and methods for assessing causesand impacts. Wallingford (UK): CABInternational and International Board for SoilResearch and Management. p 51-71.


Wade LJ. 1998. Research balance, impact deliveryand future challenges in crop-soil managementsystems. Jpn. J. Crop Sci. 67: 310-311.

Wade LJ, George T, Ladha JK, Singh U, Bhuiyan SI,Pandey S. 1998. Opportunities to manipulatenutrient by water interactions in rainfed lowlandrice systems. Field Crops Res. 56: 93-112.

Wade LJ, Quintana L, Amarante ST, Naklang K,Harnpichitvitaya D, Singh AP, Sengar SS,Parihar SS, Singh G, Wihardjaka A, Mazid MA.1998. Nutrient-water interactions in diverse soilsof the rainfed lowland rice ecosystem in Asia.In: CD-ROM Proceedings of the WorldCongress of Soil Science, 19-26 Aug 1998.Symposium 14, Paper 7. Montpellier (France).

Ying J, Peng S, Yang G, Zhou N, Visperas R.M.,Cassman KG. 1998. Comparison of high-yieldrice in a tropical and subtropical environment.II. Nitrogen accumulation and utilizationefficiency. Field Crops Res. 57(1): 85-93.

Ying J, Peng S, He Q, Yang H, Yang C, VisperasRM, Cassman KG. 1998. Comparison ofhigh-yield rice in a tropical and subtropicalenvironment. I. Determinants of grain and drymatter yields. Field Crops Res. 57(1): 71-84.

Zhang C, Peng S, Bennett J. 1998. Glutaminesynthetase of roots and leaves in response tonitrogen application at different growth stagesin field-grown rice. J. Plant Nutr. 21(4): 625-633.

Ziska LH, Moya TB, Wassmann R, Namuco OS,Lantin RS, Aduna JB, Abao E Jr, BronsonKF, Neue HU, Olszyk D. 1998. see Soil andWater Sciences.

Entomology and Plant Pathology

Alam SN, Cohen MB. 1998. Detection and analysisof QTLs for resistance to the brownplanthopper, Nilaparvata lugens, in a doubled-haploid rice population. Theor. Appl. Genet.97: 1370-1379.

Alam SN, Cohen MB. 1998. Durability of brownplanthopper, Nilaparvata lugens, resistance inrice variety IR64 in greenhouse selectionstudies. Entomol. Exp. Appl. 89:71-78.

Chen XM, Line RF, Leung H. 1998. Genomescanning for resistance-gene analogs in rice,barley, and wheat by high-resolutionelectrophoresis. Theor. Appl. Genet. 97: 345-355.

George MLC, Nelson RJ, Zeigler RS, Leung H.1998. Rapid population analysis of Magna-porthe grisea by using rep-PCR and endo-genous repetitive DNA sequences. Phyto-pathology 88: 223-229.

Heong KL. 1998. IPM in developing countries:progress and constraints in rice IPM. In:Zalucki MP, Drew RAI, White GG, editors.Pest management—future challenges.Proceedings of the Sixth Australasian AppliedEntomological Research Conference,Brisbane, Australia, 29 Sep-2 Oct 1998.Australia: University of Queensland. p 68-77.

Heong KL, Schoenly KG. 1998. Impact ofinsecticides on herbivore-natural enemycommunities in tropical rice ecosystems. In:Haskell PT, McEwen P, editors.Ecotoxicology: pesticides and beneficialorganisms. London: Chapman and Hall.p 381-403.

Heong KL, Escalada MM, Huan,NH, Mai V.1998. Use of communication media inchanging rice farmers’ pest management inSouth Vietnam. Crop Prot. 17(5): 413-425.

Luo Y, Teng PS, Fabellar NG, TeBeest DO.1998a. The effects of global temperaturechange on rice leaf blast epidemics: a simula-tion study in three agroecological zones.Agric. Ecosyst. Environ. 68: 187-196.

Luo Y, Teng PS, Fabellar NG, TeBeest DO. 1998b.Risk analysis of yield losses caused by rice leafblast associated with temperature changesabove and below for five Asian countries.Agric. Ecosyst. Environ. 68: 197-205.

Mew TW, Merca SD, Gonzales P, Guevarra J,Huelma C. 1998. Epidemiology of seed-bornefungal diseases. In: Proceedings of theInternational Workshop on Management ofSeed-borne Diseases for Food Production inthe 21st Century, 25-27 Mar 1998, NagoyaCongress Center, Japan.


Michel VV, Mew TW. 1998. Effect of a soilamendment on the survival of Ralstoniasolanacearum in different soils.Phytopathology 88: 300-305.

Ona I, Vera Cruz CM, Nelson RJ, Leach JE, MewTW. 1998. Epidemic development of bacterialblight on rice carrying resistance genes Xa-4,Xa-7, and Xa-10. Plant Dis. 82(12): 1337-1340.

Satapathy MK, Teng PS, Anjaneyulu A. 1998. Ricetungro disease and its management. In:Upadhay K, Mukerji KG, Rajak RL, editors.IPM systems in agriculture. Vol. 3. Cereals.New Delhi, India: Aditya Books Pvt. Ltd.p 105-130.

Savary S, Elazegui FA, Teng PS. 1998. Assessingthe representativeness of data on yield lossesdue to rice diseases in tropical Asia. Plant Dis.82 (6): 705-709.

Savary S, Willocquet L, Castilla N. 1998. Effectsof some environmental factors on rice sheathblight epidemiology. In: Proceedings of theInternational Conference of Plant Pathology,Edinburgh, 9-16 Aug 1998. Vol 1.

Savary S, Elazegui FA, Willocquet L, Teng PS.1998. Changing production situations in riceand implications for plant pathology. In:Proceedings of the International Conference ofPlant Pathology, Edinburgh, 9-16 Aug 1998,Vol 1.

Schoenly KG, Justo HD Jr, Barrion AT, Harris MK,Bottrell DG. 1998. Analysis of invertebratebiodiversity in a Philippine farmer’s irrigatedrice field. Environ. Entomol. 27(5): 1125-1136.

Shi Z, Christian D, Leung, H. 1998. Interactionsbetween spore morphogenetic mutationsaffect cell types, sporulation, and patho-genesis in Magnaporthe grisea. Mol. PlantMicrobe Interact. 11: 199-207.

Sigsgaard L. 1998. Natural control of Helicoverpaarmigera in sorghum-pigeon pea intercrop-ping. In: Proceedings of the Sixth Austral-asian Applied Entomological Research Con-ference, University of Queensland, Brisbane,Australia, 29 Sep-2 Oct 1998. 340 p.

Teng PS, Batchelor WD, Pinnschmidt HO,Wilkerson G. 1998. Simulation of pest effects

on crops using pest-crop models: the potentialfor decision support. In: Tsuji G,Hoogenboom G, Thornton PK, editors.Understanding options for agriculturalproduction. Dordrecht, The Netherlands:Kluwer Academic Publishing. p 225-270.

Theunis W, Aguda RM, Cruz WT, Decock C,Peferoen M, Lambert B, Bottrell DG, GouldFL, Litsinger JA, Cohen MB. 1998. Bacillusthuringiensis isolates from the Philippines:habitat distribution, δ-endotoxin diversity, andtoxicity to rice stem borers (Lepidoptera:Pyralidae). Bull. Entomol. Res. 88: 335-342.

Tiongco ER, Chancellor TCB, Villareal S,Magbanua M, Teng PS. 1998. Studies on theeffectiveness of roguing as a means ofcontrolling rice tungro virus disease. J. PlantProt. Trop. 11: 45-52.

Tu J, Ona I, Zhang Q, Mew TW, Khush GS, DattaSK. 1998. see Plant Breeding, Genetics, andBiochemistry.

Way MJ, Islam Z, Heong KL, Joshi RC. 1998. Antsin tropical irrigated rice: distribution andabundance, especially of Solenopsis geminata(Hymenoptera: Formicidae). Bull. Entomol.Res. 88: 467-476.

Xie GL, Mew TW. 1998. A leaf inoculationmethod for detection of Xanthomonas oryzaepv. oryzicola from rice seed. Plant Dis. 82:1007-1011.

Yu X, Hu C, Heong KL. 1998. Parasitization andpreference characteristics of egg parasitoidsfrom various habitats to homopterans. ActaEntomol. Sin. 41: 41-47.

Zeigler RS. 1998. Recombination in Magnaporthegrisea. Annu. Rev. Phytopathol. 36: 249-275.

Genetic Resources Center

Bellon MR, Pham JL, Sebastian LS, Francisco SR,Loresto GC, Erasga DS, Sanchez P, CaliboMA, Abrigo G, Quilloy SE. 1998. Farmers’perceptions of varietal diversity: implicationsfor on-farm conservation of rice. In: Smale M,editor. Farmers, gene banks and cropbreeding. Dordrecht, The Netherlands:Kluwer Academic Publishing. p 95-108.


Juliano AB, Naredo MEB, Jackson MT. 1998.Taxonomic status of Oryza glumaepatulaSteud. I. Comparative morphological studiesof New World diploids and Asian AAgenome species. Genet. Res. Crop Evol. 45:197-203.

Lu BR. 1998. Diversity of the rice gene pool andits sustainable utilization. In: Zhang Aolur,Wu Sugong, editors. Floristic characteristicsand diversity of East Asian plants. Beijing:China Higher Education Press and Berlin:Springer-Verlag. p 454-460.

Lu BR, Naredo MEB, Juliano AB, Jackson MT.1998. Taxonomic status of Oryzaglumaepatula Steud. III. Assessment ofgenomic affinity among AA genome speciesfrom the New World, Asia and Australia.Genet. Res. Crop Evol. 45: 215-223.

Lu BR, Naredo MEB, Juliano AB. 1998. Abiosystematic study of the genus Oryza(Poaceae). Abstract of monocots II. Sydney,Australia. p 74.

Lu BR. 1998. Diversity of rice genetic resourcesand its utilization and conservation. Chin.Biodiversity 6 (1): 63-72.

Mew TW, Merca SD, Gonzales P. Guevarra J,Huelma C. 1998. see Entomology and PlantPathology.

Morin SR, Pham JL, Sebastian LS, Abrigo G,Erasga DS, Bellon MR, Calibo MA, SanchezP. 1998. The role of indigenous technicalknowledge in on-farm conservation of ricegenetic resources in Cagayan Valley,Philippines. In: People, earth and culture. LosBaños, Laguna, Philippines: PhilippineCouncil for Agriculture, Forestry and NaturalResources Research and Development.PCARRD-NCCA Book Series No. 165.p 137-150.

Naredo ME, Juliano AB, Lu BR, Jackson MT.1998. Taxonomic status of Oryzaglumaepatula Steud. II. Hybridizationbetween New World diploids and AA genomespecies from Asia and Australia. Genet. Res.Crop Evol. 45: 205-214.

Pham JL, Sebastian LS, Sanchez P, Calibo MA,Quilloy SE, Bellon MR, Francisco SR, ErasgaDS, Abrigo G, Loresto GC. 1998. Geneticdata and analysis in the Philippines on-farm.In: Jarvis DI, Hodgkin T, editors.

Strengthening the scientific basis of in situconservation of agricultural biodiversity on-farm. Options for data collecting and analysis.Proceedings of a workshop to develop toolsand procedures for in situ conservation on-farm, 25-29 Aug 1997. Rome, Italy: Interna-tional Plant Genetic Resources Institute. p 34.

Zhang SZ, Lu BR, Hong DY. 1998. In situhybridization and its application in studies onOryza. Acta Phytol. Sin. 36(1): 87-96.

Zhang ZY, Wen J, Lu BR. 1998. The structuralfeatures of leaf epidermis in Oryza and theirsystematic significance. Acta Phytol. Sin.36(1): 8-18.

Zhu J, Gale MD, Quarrie S, Jackson, MT, BryanGJ. 1998. AFLP markers for the study of ricebiodiversity. Theor. Appl. Genet. 96: 602-611.

Information Center

Hettel GP, Hettel AA. 1998. Preserving Bhutan’sbiological heritage. Tashi Delek 3(1): 28-35.

Wallace I. 1998. Delivering information to ricescientists around the world. Inf. Dev. 14(4):198-202.

Plant Breeding, Genetics, and Biochemistry

Alam MF, Datta K, Abrigo E, Vasquez A,Senadhira D, Datta SK. 1998. Production oftransgenic deepwater indica rice plantsexpressing a synthetic Bacillus thuringiensiscryIA(b) gene with enhanced resistance toyellow stem borer. Plant Sci. 135: 25-30.

Bennett J. 1998. Balancing needs for productivityand sustainability: genetic engineering of riceat IRRI. In: Managing biotechnology in atime of transition. The Hague: InternationalService for National Agricultural Research.15 p.

Bentota AP, Senadhira D, Lawrence MJ. 1998.Quantitative genetics of rice. III. The potentialof a pair of new plant type crosses. Field CropsRes. 55: 267-273.

Brar DS, McNally RE, Mendoza R, Senadhira D,Jones M, Khush GS. 1998. Gene transfer fortolerance to biotic and abiotic stresses fromwild species into rice. In: Proceedings of theInternational Workshop on Breeding and


Biotechnology for Environmental Stress inRice. Sapporo, Japan. p 120-125.

Datta K, Tu J, Oliva N, Muthukrishnan S, DattaSK. 1998. Transgenic rice for enhancedresistance to Rhizoctonia solani causingsheath blight disease. In: Larkin PJ, editor.Proceedings of the 4th Asia-PacificConference on Agricultural Biotechnology.Darwin, Australia. p 38-40.

Datta K, Vasquez A, Tu J, Torrizo L, Alam MF,Oliva N, Abrigo E, Khush GS, Datta SK.1998. Constitutive and tissue-specificdifferential expression of the cryIA(b) gene intransgenic rice plants conferring resistance torice insect pest. Theor. Appl. Genet. 97:20-30.

Delos Reyes BG, Khush GS, Brar DS. 1998.Chromosomal location of eight isozyme loci inrice using primary trisomics and monosomicalien addition lines. J. Hered. 89:164-168.

Fahim M, Dhanapala MP, Senadhira D, LawrenceMJ. 1998. Quantitative genetics of rice. II. Acomparison of the efficiency of four breedingmethods Field Crops Res. 55: 257-266.

Hiroshi K. 1998. Development and utilization ofhybrid rice in Malaysia [in Japanese, withEnglish summary]. JIRCAS Res. Highlights5: 37-38.

Jain SM, Brar DS, Ahloowalia BS, editors. 1998.Somaclonal variation and induced mutations incrop improvement. Dordercht, The Nether-lands: Kluwer Academic Publishers. 615 p.

Julfiquar AW, Virmani SS. 1997. Inheritance ofwide compatibility trait in rice (Oryza sativaL.). Bangladesh J. Life Sci. 9(2): 1-7.

Khush GS. 1998. Strategies for increasing cropproductivity. In: Chopra VL, Singh RBAnupam Verma, editors. Crop productivityand sustainability — shaping the future.Proceedings of the 2nd International CropScience Congress. New Delhi: Oxford andIBH Publishing Co. Pvt. Ltd.. p 19-43.

Khush GS. 1998. Innovative approaches forimproving the yield and grain quality of rice.In: Lu HY, Sung JM, Kao CH, editors. AsianCrop Science. Proceedings of the 3rd AsianCrop Science Conference. Taichung, Taiwan:Chinese Society of Agronomy. p 436-450.

Khush GS, Baenziger PS. 1998. Cropimprovement: emerging trends in rice andwheat. In: Chopra VL, Singh RB AnupamVerma, editors. Crop productivity andsustainability — shaping the future.Proceedings of the 2nd International CropScience Congress. New Delhi: Oxford andIBH Publishing Co. Pvt. Ltd. p 113-125.

Khush GS, Brar DS. 1998. The application ofbiotechnology to rice. In: Eves CL, BedfordBM, editors. Agricultural biotechnology ininternational development. Wallingford, UK:CABI Publishing. p 97-121.

Khush GS, Sarkarung S. 1998. New plant type andbreeding strategies for rainfed lowland rice.In: Rainfed rice for sustainable food security.Cuttack, Orissa, India: Central Rice ResearchInstitute. p 44-52.

Khush GS, Peng SB, Virmani SS. 1998.Improving yield potential by modifying planttype and exploiting heterosis. In: WaterlowJC, Armstrong DG, Fowden L, Riley R,editors. Feeding a world population of morethan a billion people: a challenge to science.New York, USA: Oxford University Press.p 150-170.

Ladha JK, Kirk G, Bennett J, Peng S, Reddy CK,Singh U. 1998. see Soil and Water Sciences.

Lawrence MJ, Senadhira D. 1998. Quantitativegenetics of rice. IV. A breeding strategy. FieldCrops Res. 55:275-281.

Li ZK, Pinson SRM, Paterson AH, Stansel JW. 1998.Genetic dissection of the source-sink relation-ship affecting fecundity and yield in rice. Mol.Breed. 4: 419-426.

Ling DH, Tao LZ, Ma ZR, Zhang SP, Datta SK.1998. Engineered male sterile transgenicplants of rice (Oryza sativa L.) with ps1-barnase gene transformation by particlebombardment. Acta Genet. Sin. 25(5):433-442.

Peng SB, Laza RC, Khush GS, Sanico AL,Visperas RM, Garcia FV. 1998. seeAgronomy, Plant Physiology, andAgroecology.


Perera ALT, Fahim M, Sriyoheswara S, DhanapalaMP, Senadhira D, Lawrence MJ. 1998.Quantitative genetics of rice. I. Evidence ofunexploited genetic variation for yield andother quantitative characters in modern indicacultivars. Field Crops Res. 55: 245-256.

Reddy PM, Ladha JK, Ramos MC, Hernandez R,Torrizo L, Datta SK, Datta K. 1998. see Soiland Water Sciences.

Sanchez AC, Khush GS. 1998. Inheritance andlinkage relationships of twenty-one genes inrice, Oryza sativa L. SABRAO J. 30: 51-60.

Singh S, Singh ON, Singh RK, Sarkarung S. 1998.A shuttle breeding approach to rice improve-ment for rainfed lowland ecosystem in easternIndia. In: Sustainable agriculture for food,energy and industry. London: James andJames Science Publishers Ltd. p 150-155.

Subudhi PK, Nandi S, Casal C, Virmani SS,Huang N. 1998. Classification of ricegermplasm: III. High-resolution finger-printing cytoplasmic genetic male-sterile(CMS) lines with AFLP. Theor. Appl. Genet.96: 941-949.

Subudhi PK, Virmani SS, Huang N. 1998. ATGMS-linked nuclear DNA marker asoriginated from the mitochondrial genome inrice (Oryza sativa L.). Heredity 80: 285-292.

Subudhi PK, Borkakati RP, Virmani SS, Huang N.1997. Molecular mapping of thermosensitivegenetic male sterility gene in rice usingbulked segregant analysis. Genome 40:188-194.

Tu J, Datta K, Alam MF, Fan Y, Khush GS, DattaSK. 1998. Expression and function of ahybrid Bt toxin gene in transgenic riceconferring resistance to insect pests. PlantBiotechnol. 15: 183-191.

Tu J, Ona I, Zhang Q, Mew TW, Khush GS, DattaSK. 1998. Transgenic rice variety IR72 withXa21 is resistant to bacterial blight. Theor.Appl. Genet. 7: 31-36.

Virmani SS, Kumar I. 1997. Hybrid rice in AsiaPacific Region. Asian Seed 97 1(14): 1-37.

Xu J, Constantino SV, Magpantay G, Bennett J,Sarkarung S, Huang N. 1998. Classificationof rice germplasm. II. Discrimination ofindica from japonica via analysis of ampliconlength polymorphisms. Plant Cell Rep. 17:640-645.

Yang D, Sanchez A, Khush GS, Zhu Y, Huang N.1998. Construction of a BAC contig contain-ing xa5 locus in rice. Theor. Appl. Genet.97:1120-1124.

Zhang CF, Peng SB, Bennett J. 1998. seeAgronomy, Plant Physiology, andAgroecology.

Social Sciences

Dawe D. 1998. Re-energizing the GreenRevolution in rice. Am. J. Agric. Econ. 80(5):948-953.

Hossain M, Diaz CP. 1997. Reaching the poorwith effective microcredit: evaluation of aGrameen bank replication in the Philippines.Philipp. Sociol. Rev. 45(1-4): 89-119.

Kam SP, Minh VQ, Tuong TP, Hoanh CT, LiewSC, Chen P. 1998. Remote sensing and GISapproaches to studying changes in ricecropping systems in the Mekong River Delta,Vietnam. In: Proceedings of the FourthSeminar on GIS and Developing Countries,GISDECO’98, Pretoria, South Africa.

Kam SP, Hoanh CT. 1998. Implementing GIS in adecision support system for analyzing thebalance between rice supply and demand. In:Proceedings of the Fourth Seminar on GIS andDeveloping Countries GISDECO’98, Pretoria,South Africa.

Liew SC, Kam SP, Tuong TP, Chen P, Minh VQ,Lim H. 1998. Application of multi-temporalERS-2 synthetic aperture radar in delineatingrice cropping systems in the Mekong RiverDelta, Vietnam. IEEE TGARSS IGARSS’97Special issue.

Luo Y, Teng PS, Fabellar NG, TeBeest DO.1998a,b. see Entomology and PlantPathology.

Palis FG. 1998. Changing farmers’ perceptionsand practices: the case of insect pest controlin Central Luzon, Philippines. Crop Prot.17(7): 599-607.

Price LL, Palis FG. 1998. Transformations inentitlement: land ownership and farmingculture in Vietnam. Cult. Agric. 20(1): 12-20.

Pandey S, Minh D. 1998. A socio-economicanalysis of rice production systems in theupland of northern Vietnam. Agric. Ecosyst.Environ. 70: 249-258.


Pandey S. 1997. Rainfed lowland rice research:challenges and priorities for the 21st century.In: Breeding strategies for rainfed lowlandrice in drought-prone environments. ACIARProceedings No. 77. Australia: AustralianCentre for International AgriculturalResearch. p.1-12.

Pandey S, Lapar L. 1998. A microeconomic analysisof adoption of contour hedgerows in thePhilippine uplands. In: Penning de Vries FWT,Angus F, Kerr J, editors. Soil erosion at multiplescales: principles and methods for assessingcauses and impacts. Wallingford,UK: CABInternational and International Board for SoilResearch and Management. p 83-98.

Pandey S, Lapar L, Waibel H. 1998. Factorsdetermining the adoption of soil conservationpractices: some implications for sustain-ability. In: Proceedings of the InternationalConference on Sustainable Agriculture forFood, Energy and Industry. London: James &James. p 270-275.

Paris T. 1998. Technology and policy needs of poorwomen in Asian rice farming. Gender Technol.Dev. 2(2): 188-218.

Pingali PL, Hossain M, Pandey S, Price LL. 1998.Economics of nutrient management in Asianrice systems. Field Crops Res. 56:157-176.

Wade LJ, George T, Ladha JK, Singh U, BhuiyanSI, Pandey S. 1998. see Agronomy, PlantPhysiology, and Agroecology.

Widawsky D, Rozelle S, Songqing J, Huang J.1998. Pesticide productivity, host-plantresistance and productivity in China. Agric.Econ. 19: 203-217.

Soil and Water Sciences

Badaruddin M, Meisner CA, Razzaue MA,Timsina J, Bronson K, Razu RA, Hobbs P.1998. Trends in intensive rice-wheat systemsof South Asia. In: Agronomy abstracts.Madison, WI: American Society ofAgronomy. p 54.

Bijay-Singh, Bronson KF, Yadvinder-Singh,Hussain F. 1998. Chlorophyll meter-basednitrogen management for rice in Asia. In:Agronomy abstracts. Madison, WI: AmericanSociety of Agronomy. p 307.

Bronson KF, Cassman KG, Wassmann R, OlkDC, van Noordwijk M, Garrity D. 1998. Soilcarbon dynamics in different croppingsystems in principal ecoregions of Asia. In:Lal R, Kimble JM, Follett RF, Stewart BA,editors. Management of carbon sequestrationin soil. Boca Raton, Florida: CRC Press.p 35-57.

Bronson KF, Fillery IRP. 1998. Fate of nitrogen-15-labelled urea applied to wheat on awaterlogged texture-contrast soil. Nutr. Cyc.Agroecosyst. 51(2): 175-183.

Cassman KG, Peng S, Olk DC, Ladha JK,Reichardt W, Dobermann A, Singh U. 1998.see Agronomy, Plant Physiology, andAgroecology.

Clement A, Ladha JK, Chalifour FP. 1998.Nitrogen dynamics of various green manurespecies and the relationship to lowland riceproduction. Agron. J. 90: 149-154.

Damgaard LR, Revsbech NP, Reichardt W. 1998.Use of an oxygen-insensitive microscalebiosensor for methane to measure methaneconcentration profiles in a rice paddy. Appl.Environ. Microbiol. 64: 864-870.

Dobermann A, Adviento MAA, Pampolino MF,Nagarajan R, Stalin P, Skogley EO. 1998.Opportunities for in situ soil testing inirrigated rice. In: Proceedings of the 16thWorld Congress of Soil Science. Montpellier:International Society of Soil Science andCentre de cooperation internationale enrecherche agronomique pour ledeveloppement.

Dobermann A, Cassman KG, Mamaril CP, SheehyJE. 1998. Management of phosphorus,potassium and sulfur in intensive, irrigatedlowland rice. Field Crops Res. 56: 113-138.

George T, Buresh RJ, Ladha JK, Punzalan G.1998. Recycling in situ legume-fixed and soilN in tropical lowland rice. Agron. J. 90:429-437.

Kirk GJD, George T, Courtois B, Senadhira D.1998. Opportunities to improve phosphorusefficiency and soil fertility in rainfed lowlandand upland rice ecosystems. Field Crops Res.56: 73-92.


Kirk GJD, Santos EE, Findenegg GR. 1998.Phosphate solubilization by organic acidexcretion. In: Proceedings of the 16thCongress of the International Society of SoilScience. Montpellier: International Society ofSoil Science.

Kronzucker HJ, Kirk GJD, Siddiqi MY, GlassADM. 1998. Effects of hypoxia on 13NH

4

+

fluxes in rice roots: kinetics and compart-mental analysis. Plant Physiol. 116: 581-587.

Ladha JK, Kirk GJD, Bennett J, Peng S, ReddyCK, Reddy PM, Singh U. 1998. Opportunitiesfor increased nitrogen use efficiency fromimproved rice germplasm in lowland riceecosystems. Field Crops Res. 56: 41-71.

Ladha JK, Padre AT, Punzalan GC, Castillo EG,Singh U, Reddy CK. 1998. Non-destructiveestimation of shoot nitrogen in different ricegenotypes. Agron. J. 90: 33-40.

Minh LQ, Tuong TP, Van Mensvoort MEF,Bouma J. 1998. Soil and water tablemanagement effects on aluminum dynamicsof an acid sulphate soil. Agric. Ecosyst.Environ. 68(3): 255-262.

Razafinjara AL, Kirk GJD. 1998. Interactionsbetween silicon and ammonium-versus-nitratenutrition in rice. In: Proceedings of the 16thCongress of the International Society of SoilScience. Montpellier: International Society ofSoil Science.

Reddy PM, Ladha JK, Ramos MC, Hernandez R,Torrizo L, Datta SK, Datta K. 1998. Nodfactors activate MtENOD12 gene expressionin rice. Plant J. 14: 693-702.

Reddy PM, Kouchi H, Ladha JK. 1998. Isolation,analysis and expression of homologues of thesoybean early nodulin gene GmENOD93(GMN93) from rice. Biochem. Biophys. Acta91214: 1-7.

Reichardt W. 1998. Sustainability based onmicrobe-mediated nutrient-supplyingcapacities in tropical rice systems, In: BassamNL, Behl RK, Prochnow B, editors.Sustainable agriculture for food, energy, andindustry. Strategies towards achievement.Vol. 1. London, UK: James & James SciencePubl. Ltd. p 466-469.

Sethunathan N, Neue HU, Parashar DC,Wassmann R, Rao VR, Adhya TK,Ramakrishnan B. 1998. Greenhouse effectand mitigation options. In: Mohanty SK et al,editors. Rainfed rice for sustainable foodsecurity. Cuttack, India. p 409-424.

Shrestha RK, Ladha JK. 1998. Nitrate ingroundwater and integration of nitrogen-catchcrop in intensive rice-based system. Soil Sci.Soc. Am. J. 62: 1610-1619.

Singh U, Ladha JK, Castillo EG, Punzalan G,Tirol-Padre A, Dequeza M. 1998. seeAgronomy, Plant Physiology, andAgroecology.

Tuong TP, Bhuiyan SI, Guerra LC, Barker R. 1998.Technology and management practices forincreasing water productivity in rice-basedsystems: growing more rice with less water. In:Water in 2000—efficient operation and manage-ment of irrigation systems. Proceedings of the1998 World Day Symposium, Seoul, Korea, 20Mar 1998. Seoul: Korean National Committeeon Irrigation and Drainage and Rural Develop-ment Corporation. p 37-88.

Tuong TP, Minh LQ, Ni DV, Van MensvoortMEF. 1998. Reducing acid pollution fromreclaimed acid sulphate soils: experiencesfrom the Mekong Delta, Vietnam. In: PereiraLS, Gowing J, editors. Water and the environ-ment, innovation issues in irrigation anddrainage. Selected papers from the 1st Inter-regional Conference on Environment-Water:Innovative Issues in Irrigation and Drainage,Sep 1998, Lisbon, Portugal. Lisbon:Portuguese National Committee of theInternational Commission on Irrigation andDrainage. p 75-83.

Wade L, Bhuiyan SI, Dobermann A, George T,Kirk GJD, Kondo M, Ladha J, Pandey S,Singh U, Tuong TP, Zeigler RS. 1998. seeAgronomy, Plant Physiology, andAgroecology.

Wassmann R, Neue HU, Bueno C, Lantin RS,Alberto MCR, Buendia LV, Bronson K,Papen H, Rennenberg H. 1998. Inherentproperties of rice soils determining methaneproduction potentials. Plant Soil 203: 227-237.


Ziska LH, Moya TB, Wassmann R, Namuco OS,Lantin RS, Aduna JB, Abao E Jr, BronsonKF, Neue HU, Olszyk D. 1998. Long-termgrowth at elevated carbon dioxide stimulatesmethane emission in tropical paddy rice.Global Change Biol. 4: 657-665.

Rice research seminars

Host plant resistance to the brown planthopper:where do we go from here? Dr. M. B. Cohen.

Advances in development and use of hybrid ricetechnology for shifting the yield frontier.Dr. S. S. Virmani.

Communicating pest management to millions–acase study in the use of printed materials andradio in Vietnam. Dr. K. L. Heong.

Ok, I know it’s fun to surf but–how can I use theinternet for real work?: exploiting thepotential of the internet for communication,information dissemination, and training.Dr. R. Raab and Mr. I. Moore.

Genetic studies on blast resistance in rice: IRRI-Japanese government collaborative project.Mr. T. Imbe.

Molecular mapping and marker-aidedbackcrossing of two bacterial blight resistancegenes to the new plant type of rice.Dr. A. Sanchez.

Biodiversity, discovery, molecular screening, andpatenting. Dr. L. Lange, senior principalscientist, Novo Nordisk A/S, Bagsvaerd,Denmark and member, IRRI Board ofTrustees.

Functions of the organic matter phase in wetlandrice soils: a promising target for soil qualityassessments? Dr. W. Reichardt.

Novel rapid methods for genomic sequencing.Dr. W. Szybalski, professor of oncology,McArdle Laboratory for Cancer Research,University of Wisconsin Medical School,Madison, Wisconsin, USA, and founder/honorary editor (and former editor-in-chief)of the journal “Gene.”

The database for extrapolating methane emissionsfrom rice fields. Dr. R. Wassmann.

Managing the world’s largest collection of ricegenetic resources. Dr. M. Jackson.

Why we need the International Network forGenetic Evaluation of Rice (INGER).Dr. S.-W. Ahn.

Genetic conservation: the role of rice farmers.Dr. J.-L. Pham.

Rice variety classification among rice farmers inthe Cagayan Valley, Philippines: its utility foron-farm conservation. Dr. S. Morin.

Understanding the biosystematic relationships ofwild rices. Dr. B. Lu.

Disease resistance, rice mutants, and functionalgenomics. Dr. H. Leung.

The ecology of plant virus disease. Dr. M. Thresh,chairman, Virus Epidemiology Committee,International Society of Plant Pathologists,UK.

Plant breeding perspectives: balanced integrationof approaches. Dr. A. Ashri, Jacob and RachelLiss professor of agronomy, Faculty ofAgriculture, The Hebrew University ofJerusalem, Israel.

Operationalizing the ecoregional approach in theUplands of the Red River Basin. Dr. J-C.Castella.

Juggling science and management: seven years inthe IRRI circus. Dr. R.S. Zeigler.

Division seminars

Agronomy, Plant Physiology, andAgroecology

Weeds and crop production systems—a NewZealand perspective. Dr. K. Harrington,senior lecturer, Massey University, NewZealand.

Methods in allelochemical discovery. Dr. A.Rimando, chemist, U.S. Department ofAgriculture

Modeling integrated weed management in direct-and water-seeded rice agroecosystems.Dr. B.P. Caton.

A multiscale approach to on-farm erosionresearch: application to north Thailandhighlands. Dr. G. Trébuil.

Allelopathy in rice. Dr. M. Olofsdotter.Nitrogen availability in lowland rice soils. I. New

research tools. II. Update on the rice-uplandcrop rotation field trial. Dr. D. Olk andMs. M. Samson.


Plant hormones and their application inagricultural production. Prof. H. Saka,University Farm, Tokyo University, Japan.

Ethylene-induced shoot elongation: a mechanismto avoid flooding stress. Prof. R. Voesenek,University of Nijmegen, The Netherlands.

Photosynthate partitioning in rice and other studiesof agro-environmental relevance. Prof. N.N.Barthakur, McGill University, Canada.

Water stress and productivity: expansive growthof roots vs leaves, radiation interception inrelation to canopy photosynthesis, andreproduction and harvest index. Prof. T.C.Hsiao, University of California at Davis,USA.

Plant breeding strategies for rainfed lowland ricein northeast Thailand and Laos. Dr. S. Fukai,University of Queensland, Australia.

Source-sink relations and grain filling of ricevarieties. Dr. Jianchang Yang.

Entomology and Plant Pathology

Bt rice for control of yellow stem borer: initialimpressions. Dr. J.S. Bentur.

Evaluation of a cryIAb-transformed Iranian ricevariety against lepidopterous pests and crylAbresistance development in striped stem borer.Dr. F. Alinia.

Prey-mediated and direct effects of Bt proteins onimmature Chrysoperla carnea. Dr. A.Hilbeck, Swiss Federal Research Station forAgroecology and Agriculture.

Engineering resistance against bacterial blight ofrice. Dr. Wen Yuan Song, University ofCalifornia at Davis, USA.

Plant Breeding, Genetics, and Biochemistry

Comprehensive applications of DNA markers torice improvement and genome research—future research focus of GML. Dr. ZhikangLi.

Prospects and challenges of commercializinghybrid rice technology through private sectorin India. Mr. I. Kumar, general manager,Hybrid Rice International, Hyderabad, India.

Mapping genes controlling drought resistance inrice: progress, problems, and prospects.Dr. A. Price, lecturer, University of Aberdeen,United Kingdom.

Doubled haploid production in wheat. Dr. N.Darvey, senior lecturer, Plant BreedingInstitute, University of Sydney at Cobbity,Camden, Australia.

The CGIAR Micronutrient Project: progress inbreeding nutritionally superior staple. Dr. R.Graham, visiting scientist and professor, PlantScience University of Adelaide, and scientificcoordinator, CGIAR Micronutrient Project.

Detection of single-copy genes by fluorescent insitu hybridization (fish) and measurement of acopy number by extended DNA fiber fish.Dr. K. Fukui, Rice Genetic EngineeringLaboratory, Hokuriku National AgriculturalExperiment Station, Joetsu, Japan.

New rice for Africa. Dr. M. Jones, plant breeder,West Africa Rice Development Association,Bouaké, West Africa.

Induced mutations in breeding—modification andimprovement of industrial crops. Dr. A.Ashri, Jacob and Rachel Liss professor ofagronomy, The Hebrew University ofJerusalem, Rehovot, Israel.

Projects on genetic transformation at the Centerfor Applied Plant Molecular Biology at theUniversity of Hamburg. Prof. H. Lorz, Centerfor Applied Plant Molecular Biology,University of Hamburg, Germany.

Approaching hidden cells: egg cells, zygotes, andearly embryogenesis of wheat and barley.Prof. H. Lorz, Center for Applied PlantMolecular Biology, University of Hamburg,Germany.

Plant biotechnology and molecular breeding inGermany—problems and prospects. Prof. H.Lorz, Center for Applied Plant MolecularBiology, University of Hamburg, Germany.

Social Sciences

Hybrid rice in India’s food economy of the 21st

century. Dr. J. Janaiah, Directorate of RiceResearch, Hyderabad, India.


People’s strategies of survival due to environ-mental changes, changes in resource use, andincrease in population in two villages in theuplands of north Vietnam. Mr. C. Alther.

Effect of technology transfer programparticipation on small farmers in Chile.Dr. C. Edmonds.

Should the Philippines import or produce ricedomestically? (A study of comparativeadvantage in rice production). Dr. J. Estudilloand Dr. M. Hossain.

Farmers’ field school: IPM knowledge andfarmers’ efficiency: a case study in Iloilo,Philippines. Dr. A. Rola, director, Institute ofStrategic Planning and Policy Studies,College of Public Affairs, University of thePhilippines Los Baños.

A socioeconomic study of land use and cropproduction systems in Bac Yen District,uplands of northern Vietnam. Mr. T. Blohm,collaborative research fellow, University ofHanover.

Soil and Water Sciences

On-farm evaluation of crop productivity and soilnitrogen-supplying capacity in a rice-wheatcropping system in Nepal. Dr. C. Adhikari.

Agriculture and fertilizer scenario in India. Dr. V.Kumar.

The role of rice roots in methane production andemission. Mr. Lu.

Using crop simulation models to determinefertilizer applications in precision agriculture.Dr. R. Matthews.

Physical and chemical characterization of soilorganic matter. S. Suhi.

How to use ASL. Ms. B. Mandac.Iodine, rice, and health. Dr. R. Graham.Modeling of N mineralization and immobilization

in a flooded peat soil. Dr. P. Bloom.Spatio-temporal variability of acid sulfate soils in

the plane of reeds: impact of soil properties,crop husbandry, and water management onthe growth and yield of rice in relation tomacro-topography. Dr. O. Husson, CIRADVietnam.

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program report for 1998

Documents