international rice research newsletter vol.15 no.3

IRRN GUIDELINES The International Rice Research Newsletter objective is:

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based cropping systems. This publication will report what scientists are doing to increase the production of rice, inasmuch as this crop feeds the most densely

in the world ... IRRN is a mechanism to help rice scientists keep each other informed of current research findings."

technology for rice and for rice-

populated and land-scarce nations

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The International Rice Research Newsletter is a compilation of brief reports of current research on topics of interest to rice scientists all over the world. Contributions should be reports of recent work and work-in- progress that have broad, pan-national interest and application. Only reports of work conducted during the immediate past three years should be submitted.

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recognized terms to describe rice

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Categories of research published

GERMPLASM IMPROVEMENT genetic resources genetics breeding methods yield potential grain quality pest resistance

diseases insects other pests

stress tolerance drought

adverse temperature excess water

adverse soils integrated germplasm improvement

irrigated

upland

seed technology

rainfed lowland

deepwater tidal wetlands

CROP AND RESOURCE MANAGEMENT soils soil microbiology physiology and plant nutrition fertilizer management

inorganic sources organic sources

crop management integrated pest management

diseases insects weeds other pests

water management farming systems farm machinery

economic analysis

ENVIRONMENT

SOCIOECONOMIC IMPACT

EDUCATION AND COMMUNICATION

RESEARCH METHODOLOGY

postharvest technology

CONTENTS GERMPLASM IMPROVEMENT

Genetic resources 5 Sheath blight (ShB) resistance in wild rices 5 Panicle and grain characters of some glaberrima cultivars in Sierra Leone

Genetics 6 Inheritance of response to gibberellic acid (GA3) in semidwarf rices

Breeding methods 7 A high-yielding early hybrid rice with multiple resistance 7 Effect of gibberellic acid on pathogen infection in hybrid rice seed 8 Screening rices for good panicle exsertion

Yield potential 8 Genetic studies on rice flag leaf weight and midrib and side vein thickness 9 Photoperiod sensitivity of traditional rice variety of Andamans 9 Association of rice ratooning ability and vigor with grain yield

10 Effect of leaf senescence and stubble carbohydrate content on ratoon rice yield

10 Effect of high humidity and low temperature on spikelet fertility in indica rice

Pest resistance—diseases 11 Some components of partial resistance to blast (B1) in indica rices 12 Analysis of rice blast (Bl) pathogen virulence in Egypt 12 Resistance to blast (Bl) in Egyptian rice varieties 13 Changes in rice leaf pigment due to tungro (RTV) infection 13 Development of kresek symptoms on some rice varieties 14 Resistance of wild rices to bacterial blight (BB)

Pest resistance—insects 14 Biology of rice leaffolders (LF) on susceptible IR36 and resistant TKM6 15 Rearing yellow stem borer (YSB) for screening varietal resistance 15 MDU3, a new gall midge-resistant rice 16 Using rice nurseries to collect thrips for use in screening rice germplasm

Pest resistance—other pests 16 Reaction of rice cultivar Faro 11 to sugarcane cyst nematode Heterodera

sacchari

Stress tolerance—adverse temperature 17 Promising cold-tolerant and high-yielding rice lines for Ndop Plain,

18 Performance of cold-tolerant varieties in western hills of Nepal 18 Screening rice for temperature tolerance in northern Nigeria

Stress tolerance—adverse soils 19 Phosphorus activity in genotypes with low phosphoms tolerance

Integrated germplasm improvement 20 IET6666, a new high-yielding rice variety for Assam 20 Performance of IR46 and IR10781-143-2-3 under transplanted rainfed

Northwest Camemon

lowland conditions in Nepal

Seed technology 21 Using electrical conductivity to determine maturity stage for quality

21 Mid-storage correction to prolong viability of rice seeds rice seeds

CROP AND RESOURCE MANAGEMENT

Soil microbiology 22 Influence of wild plant and crop residues on rice yield 22 Effect of seeding rate on dry matter production and nitrogen accumulation

of Sesbania rostrata

Physiology and plant nutrition 23 Effects of a growth regulator on rice seedling growth

Fertilizer management 23 Greenhouse evaluation of urea supergranules (USG) containing

24 Rate and time of N application for direct seeded irrigated rice 25 Influence of modified urea and placement on N use in irrigated rice 25 Influence of modified urea materials at different N rates on estimated

26 Contribution of flood siltation to boro rice yield and response to N and K 27 Response of rice to Azospirillum brasilense and organic manures on

diammonium phosphate (DM) for transplanted rice

wetland rice soil ammonium-N and nitrate-N

organic- and chemical-few farms in India

Crop management 28 Effect of traditional and improved nursery methods on seedling growth

and rice yield

Integrated pest management—diseases 28 Nonfluorescent Pseudomonas strains causing rice sterility and grain

29 F alse smut incidence on rice relative to plant characters and environmental

30 Bakanae and foot rot of rice in Punjab, Pakistan 30 Efficacy of ethofenprox in preventing rice tungro (RTV) infection

Integrated pest management—insects 30 Mutual interference among wolf spider adult females 31 Fluctuation of yellow stem borer (YSB) populations in Raichur,

31 Toxicity of insecticides to mirid bug predator of rice brown planthopper 31 Feeding and food assimilation by two species of rice leaffolders (LF) on

32 Mass rearing of a mirid predator

Integrated pest management—weeds 33 Weed control in dry and wet seeded irrigated rice 33 Effect of time and number of weedings on direct seeded upland rice yields 34 Weed composition in dry seeded wetland rice

Farming systems 34 Intercropping following rice 34 Rice-based cropping systems for rainfed lowland conditions 35 Production potential and economics of upland rice + pigeonpea 36 Rice-based intercropping systems for rainfed upland conditions of

36 Some transplanted rice-based cropping systems 37 Water requirement for peanut following rice in Bangalore 37 Rice variety to fit cropping patterns in Tripura, India 37 Relay cropping in upland rice fallows

discoloration in Colombia

factors

Kamataka, India

selected weed plants

Chotanagpur plateau

GERMPLASM IMPROVEMENT Genetic resources

Sheath blight (ShB) in existing rice cultivars. To identify resistance in wild rices additional sources, we tested 76 wild rice

accessions in IRRI’s ShB nursery. (Some A. D. Amante, R. de la Pena, L. A. Sitch, H. accessions were represented by more than Leung, and T. W. Mew, IRRI one source, giving a total of 106 entries.)

Seedlings were planted in two 50-cm Development of host resistance to ShB, rows at 5 hills/row, spaced 10 cm caused by Rhizoctonia solani, has been between hills and 20 cm between rows. hampered by limited sources of resistance Inoculum (a 10- to 14-d-old culture of

Wild rices with resistance or moderate resistance to the ShB pathogen Rhizoctonia solani. IRRI, 1990.

Species Plants Plant Lesion IRGC tested height height RLH a Grade b

accession no. (no.) (cm) (cm)

O. nivara 103422 3 103835 3 103 840 3 101971 1 104444 1 104473 2 101 193 1 103841 3 103841 1 103824 1 104705 1 101967 1 101973 1 100898 1

O. barthii 101827 3 104304a 2 104304a 1 104304b 1 101317 3

O. perennis 104765 2 104822 2 104796 2 100969 1 103848 1 100692 2 104754 2 104782 1 104766a 3 104642 2 104822 1

100907 1 100907 2

100966 1 100964 1

O. rufipogon

O. latifolia

O. minuta 101089 1 IR58 (susceptible check)

127.8 119.6 126.7 130.1 113.9 120.2 100.7 114.0 122.1

91.2 108.0 120.4 124.2 101.0

88.0 92.1 95.2 99.0 98.6

172.3 109.8 115.3 135.1 106.5 107.8 93.4

130.0 124.9

86.2 104.4

120.8 154.7

127.8 122.0

93.2 77.7

39.4 36.4 36.3 38.6 34.1 35.0 26.6 31.4 33.6 25.2 28.9 32.2 31.0 23.6

26.0 23.8 22.5 22.3 22.0

34.8 31.8 32.4 37.4 29.4 28.5 24.5 34.0 31.6 19.3 24.4

26.8 31.0

30.6 33.0

17.9 32.0

30.2* 30.1 * 29.3 29.3 29.3 28.7* 27.4* 27.3** 27.2* 26.8* 26.5 26.5 25.0* 22.8**

29.5 25.3* 23.0* 22.0** 21.7**

30.0 28.3* 27.8* 27.8* 27.6 26.2* 26.0* 25.8* 24.4** 23.4* 23.0*

21.5* 19.5*

23.5* 26.5

18.7** 41.2

3 3 3 3 3 3 3 3 3 3 3 3 3 3

3 3 3 3 3

3 3 3 3 3 3 3 3 3 3 3

3 1

3 3

1 5

a * and ** = significantly different from susceptible check at 5% and 1 % level by LSD test. b 1 = resistant. 3 = moderately resistant, 5 = moderately susceptible.

R. solani in a rice hull and grain medium (3:1 vol/vol) was placed between the tillers at the base of each plant 45 and 65 d after seeding. Disease reaction was scored 15-20 d after flowering and relative lesion height (RLH = lesion height [cm]/plant height [cm] × 100) computed.

Although all entries showed ShB symptoms on the leaf sheath, about one-third (35 entries) were more resistant than susceptible check IR58 (see table). On the basis of RLH, O. minuta Acc. 101089 (RLH = 18.7%) and O. rufipogon Acc. 100907 (RLH = 19.5%) were resistant; 34 other entries were moderately resistant. These accessions may be useful donors of ShB resistance for rice improvement.

Panicle and grain characters of some glaberrima cultivars in Sierra Leone

M. S. Jusu and S. S. Monde Rice Research Station, Rokupr, Sierra Leone

A large number of subsistence farmers in Sierra Leone cultivate Oryza gluberrima because of its wide adaptability to stress, high weed competitiveness, and good eating qualities.

Evaluation of cultivars collected during the last 3 yr indicates consider- able phenotypic variation.

We evaluated 60 O. glaberrima varieties collected in Jan 1988 from upland fields in the Southern Province for variations in morphological and agronomic characters.

ate, panicle type open, and secondary branching rare (Table 1). Threshability was easy (this is a major defect in glaberrimas).

Panicle length, grain length, and grain shape varied widely (Table 2). Panicles 25 cm and longer occurred in Accessions 5886 (Pa China), 5568 (Pa

Panicle exsertion tended to be moder-

IRRN 15:3 (June 1990) 5

Table 1. Panicle and grain characters of some Oryza glaberrima cultivars. Sierra Leone, 1988.

Panicle exsertion Panicle type Secondary branching Panicle threshability Seed coat color IRRI scale Description Accessions Description Accessions Description Accessions Description Accessions Description Accessions

(%) (%) (%) (%) (%)

0 1 Well exserted 23.3 Compact 0.00 Light 5.0 Difficult 1.7 White 1.7 2 3 Moderately 41.7

4 5 Just exserted 35.0 Intermediate 15.0 6

Absent 95.0

Heavy 0.00 – – Light brown 3.3 Speckled 10.0 brown Brown 71.6

Intermediate 1.7 Red 0.0 Variable 11.7

exserted

7 Partially 0.0 exserted

purple Purple 1.7

9 Fully exserted 0.0 Open 85.0 – – Easy 96.6

Table 2. Distribution of some panicle and grain characters of some O. glaberrima Cultivars, Sierra Leone, 1988.

Character Range (%)

Panicle length 15-20 5 (cm) 20-25 87

25 & above 8 Dehulled grain length Medium (5.51 to 2

Long (6.60 to 38

Extra long (more 60

Accessions

(mm) 6.60 mm)

7.50 mm)

than 7.50 mm) Grain length: width ratio Medium (2.1 to 3.0) 12

Slender (>3.0) 88

Kamara), 5620 (Pa D.C.), 5838 (Pa Keble), 5290 (Walei), and 5839 (Pa Temne). Accession 5886 (Pa China) also showed some secondary branching and low threshability.

Genetics

Inheritance of response to gibberellic acid (GA 3 ) in semidwarf rices

Xu Jianlong and Shen Zongtan, Agronomy Department, Zhejiang Agricultural Univer- sity, Hangzhou; and Lin Yizi, Plant Institute, Zhejiang Academy of Agricultural Science, Hangzhou, China

Five semidwarf varieties (plant height about 65=90 cm), keng type, with sd 1 or sd s gene, were analyzed for heritability of response to GA 3 , Cheng-Tu-232, Jia-

23, and C2123 (with sd 1 gene) were 10 d after spraying. sensitive to GA 3 ; Xue-He-Ai-Zao and In five combinations, all F 1 s were Xue-4 (with sd s gene) were insensitive. sensitive to GA 3 (the F 1 of Xue-He-Ai-

Evenly germinating seeds were sown Zao/Xue-4 was missing). The F 2 s in 50- × 20- × 15-cm plastic trays and segregated (Fig. 1). The genotypes of sprayed with 20 ppm GA 3 solution the Sd 1 -Sd 8 - and sd 1 sd 1 Sd 8 - were sensitive; the next day. Seedling height was measured genotypes of Sd 1 -sd 8 sd 8 and sd 1 sd 1 sd 8 sd 8

1. Frequency distribution of responses of different crosses to GA 3 .

– – –

– – –

– – –

–

– – –

–

– – – –

– – – –

– – – – – – – – – –

– – –

6 IRRN 15:3 (June 1990)

2. Response of generations of Cheng-Tu-232/Xue-He-Ai-Zao to GA 3 . P 1 = Cheng-Tu-232, P 2 = Xue-He-Ai-Zao, F 1 = P 1 /P 2 , DW= dwarf.

were insensitive, at a 3:1 ratio (9 Sd 1 -Sd 8 -

The F 2 of Xue-He-Ai-Zao/Xue-4 did not segregate and was insensitive.

Dwarf plants (height less than 40 cm),

:3 sd 1 sd 1 Sd 8 :3 Sd 1 -sd 8 sd 8 :1 sd 1 sd 1 sd 1 sd 8 ). probably having both sd genes, were found in the F2 of every combination (Fig. 2). Response of the dwarfs was similar to that of Xue-He-Ai-Zao.

Breeding methods

A high-yielding early hybrid rice with multiple resistance

Zheng Lingxiang and Tang Hongjing, Institute of Rice, Guizhou Academy of Agricultural Sciences, Guiyang, China

Wei-you 481 is a newly released early indica hybrid of V20A/Qian-hui 481.

Qian-hui 481 is an isocytoplasmic R-line derived from Zhen Xian 97A/Tai Yin 1// Xiankengnuo///Gui 6/IR26////IR24/ Liuganjianye (an indica/japonica combination). Indica varieties Tai Yin 1 and IR26 have bacterial blight (BB) resistance and IR24 and IR26 have blast (B1) resistance in Guizhou. Japonica varieties Liuganjianye and Xiankengnuo (a

Table 1. Some agronomic characteristics a of Wei-you 481, Guizhou, China.

Duration Plant Panicles Grains 1,000- Seed Yield Yield/d Variety (d) ht (no./m 2 ) (no./ grain set (t/ha) (kg/ha)

(cm) panicle) wt (g) (%)

Wei-you 481 162 88.5 342.0 118.2 27.0 78.2 8.4 52.2 Wei-you 64 153 76.7 394.5 108.5 28.4 77.5 7.7 51.1

a Mean of 4 rites (1100-1500 m above sea level) in the regional trials of hybrid rice in Guizhou Province, 1987.

Table 2. Reaction a of Wel-you 481 to B1, BB, and cold, Guizhou, China, 1987.

Reaction to B1 Reaction Reaction to cold Variety

Leaf B1 Neck B1 to

BB Seedling stage Flowering stage b

Wei-you 481 2.0 1.5 3.0 3.0 ++ wei-you 64 4.5 5.0 7.0 7.0 +

a Mean of 4 test sites in Guizhou Province. Scoring according to Standard evaluation system for rice scale: 0-9. b + = moderate cold resistance, ++ = strong cold resistance.

Guizhou indigenous variety) have strong cold tolerance.

Wei-you 481 performed well in 1988 regional trials for single, mid-season rice cropping areas 1,100-l,500 m altitude in Guizhou Province. Average yields were 8.4 t/ha, 9% higher than that of popular hybrid rice Wei-you 64 (Table 1).

An outstanding characteristic of Wei- you 481 is its multiple resistances (Table 2). In artificial inoculation tests in 1988, it was resistant to 102 Pyricularia oryzae isolates belonging to 21 races.

Effect of gibberellic acid on pathogen infection in hybrid rice seed

Zhou Zhongyue, Tang Shande, and Mo Zhijun, Lingling Agricultural School, Hunan, China

Hybrid rice seed may be infected with glume spots caused by pathogens, primarily Alternaria, and kernel smut caused by Tilletia barclayana. Serious infection results in low seed viability.

We studied the effect of six levels of gibberellic acid (GA3) spray on incidence of glume spots and kernel smut on hybrid seed produced on CMS line V20A. The experiment was laid out in a randomized complete block design with three replications. Both glume spots and kernel smut incidence decreased with GA 3 application (see table). Application

Effect of GA 3 application on pathogen infection of hybrid rice seeds. a Hunan, China, 1988.

GA 3 level Glume spot Kernel smut (g/ha) (%) (%)

0 44.0 d 22.1 b 90 25.0 b 6.0 a

180 23.9 a 7.7 a 240 23.4 a 360

3.9 a 26.5 c

450 6.8 a

27.6 c 4.8 a

a In a column, mean followed by difficult letters are significantly different at the 5% level (DMRT).

level did not show significant differences in kernel smut incidence, but glume spots decreased up to 240 g GA3/ha. Higher application increased glume spot incidence.

IRRN 15:3 (June 1990) 7

Screening rices for good panicle exsertion

S. Jebaraj, S. Palanisamy, and M. Subrama- nian, Agricultural Botany Department, Agricultural College and Research Institute, Madurai 625104, Tamil Nadu, India

We evaluated panicle exsertion in 40 genotypes, including 4 commonly cultivated medium-duration rice varieties, during 1987 wet season (Jun-Sep). The experiment was laid out in a randomized block design with two replications.

Three plants/replication were selected

randomly at the end of 50% flowering. Panicle exsertion was measured as the distance between the place of emergence of the flag leaf to the base of the panicle.

The varieties studied showed highly significant differences in panicle exsertion. Exserted panicle length varied from 1.60 to 10.95 cm, with a 40% coefficient of variation (see table). T414, 864, 916, 979, 1037, 2253, 2256, 2292, 2699, 2710, 2730, and 2869 had significantly better exsertion.

male-sterile lines with well-exserted panicles for hybrid seed production.

These types could be used to develop

Panicle exsertion in different rice varieties. a Tamil Nadu, India, 1987 wet season.

Mean

length (cm) Type Variety Origin exsertion

T23 Safeda Central province 6.33

T864 Kesse-Koyoba (m) West Africa (Gambia) 9.75 T414 Long grain, awned Madurai 7.76

T916 V. Melonoceros Kore Russia 6.90 T951 Matali Punjab 2.18 T979 Ichabtsi China 9.27 T1004 Sauchaotsi China 6.14 T1037 III 14-8 China 9.78 T1403 Thavalaikannan Malabar 4.01 T1418 Gudumaskathi S. Canara 6.33 T1621 Dc. Sierrikone Africa 5.92 T1651 Madaoliso Brazil 1.71 T1745 Senkar Udumalpet 5.83 T2253 Lati Amtoo Mohar (157) Bombay 7.15 T2256 Banaspatri (Medium) Lashkar (Gwalior) 10.95 T2292 Kalomashine Kalitong, Assam 10.55 T2337 Nira USA 3.65 T2402 CP15 CRRI, Cuttack 6.60 T2408 Cuttack 10 Aikoku CRRI, Cuttack 4.94 T2436 China 62 China 5.52 T2613 Chungnung No. 4 China 5.71 T2669 Varylava Ali Combo Madagascar 6.16 T2684 Tainan 1 Japonica - Taiwan 5.51 T2688 Kaohsiung 64 Japonica - Taiwan 5.18 T2690 Irradiated Taichung 65 Japonica - Taiwan 5.23 T2699 (CP231/3 *Bluebonnet)/PI215936 9.50 T2706 PI 215936/CI 9214 6.11 T2710 PI 215936/CI 9214 9.50 T2717 CI 9402 (CP23 1/Bluebonnet) 5.71 T2721 (PI 215936/CI9214) 4.78 T2729 CI 9155/(C.50/Kh.27) 4.08 T2730 Hsinchu 50 Taiwan 10.11 T2811 Cuttack 45 (Ch.45/AC 1951) Cuttack 4.43 T2842 14 E. Punjab 2.54 T2845 1206-17-21 Maharashtra 4.46 T2869 Takao Taiwan 7.00

IR20 Philippines 4.18 Ponni Malaysia 5.98 Co 43 Coimbatore 1.60 Co 44 Coimbatore 2.94

Overall mean 6.05 LSD 0.83 CV = 40.3 1 %

a Underlined values a significantly better than overall mean. F test significant at 1 % level.

Yield potential Genetic studies on rice flag leaf weight and midrib and side vein thickness

Shen Fu-Cheng and Liu Chuang-Xiu, Guizhou Academy of Agricultural Sciences, Guizhou Province, China

Thicker rice leaves have been found to have higher photosynthetic rates. Some studies have related photosynthetic rate to the diameter of the leaf vascular bundles.

We studied the heritability of specific flag leaf weight (SLW), midrib thickness (TMR), and side vein thickness (TSV) at heading in parental and F 2 populations of Guichao 2/82-856 and Conggui 226/82- 856. Vein thickness was measured by micrometer. Flag leaf area (A) was measured as

A = 2/3L 1 L 2 +1/3L 3 (L 1 -L 4 )

where L 1 = leaf length, L 2 = leaf greatest width, L 3 = leaf basal width, and L 4 = leaf length from the widest part to the pointed end.

Variety 82-856 had very thick leaves (SLW = 10.027 mg/dm 2 , TMR = 78.07 mm, TSV = 38.51 mm). Guichao 2 and Conggui 226 had thinner leaves (for Guichao 2, SLW = 6.03 mg/dm2. TMR = 41.47 mm, TSV = 23.80 mm; for Conggui 226, SLW = 6.227 mg/dm2, TMR = 45.70 mm, TSV = 23.89 mm).

Leaf heritability ( h2 ) was calculated as

WF 2 -1/2(VP 1 +VP 2 ) h 2 =

VF 2

× 100

All F 1 values for TMR, TSV, and SLW in both combinations were between the two parents (see figure). The F 2 distributions for SLW and TSV were continuous and almost abnormal in both combinations. Distributions for TMR were skewed, showing predomi- nance of the lower segregants, in both combinations. Heritabilities were SLW>TMR>TSV. For Conggui 226/82- 856, heritabilities were 78.63% for SLW 62.06% for TMR, and 27.10% for TSV. For Guichao 2/82-856, heritabilities were

8 IRRN 15:3 (June 1990)

- - - - - -

- - - -

2. Variation in daylength and temperature during different months in Port Blair, India.

of CR1009 was about 65 d and that of C14-8 80 d. The photoperiod-sensitive phase was about 30 and 226 d, respectively.

The marked difference in flowering durations with month of sowing is attributed mainly to response to varying daylengths in different months (Fig. 2). Variation in days to flowering was caused by difference in vegetative lag phase only. The basic vegetative, reproductive, and ripening phases were constant in both varieties.

C14-8 is highly sensitive to slight variations in daylength, indicating strong photoperiod sensitivity.

F 2 distribution of TMR, TSV, and SLW in the cross of Guichao 2/82-856F 2 .

72.52% for SLW, 66.19% for TMR, and 33.84% for TSV.

This suggests that SLW and TSV had multigenic and additive actions and that

TMR was controlled by some major genes and a small number of dominant genes with cumulative and unequal effect.

Photoperiod sensitivity of traditional rice variety of Andamans

S. Singh and T. Ram, Central Agricultural Research Institute, Port Blair 744101, India

Local rice variety C14-8 occupies more than 50% of the rice area in Andamans. We compared its photoperiod sensitivity

with the moderate photoperiod sensitivity of modern variety CR1009 at 12° N lat. and 92-94° E long. The crops were sown on the 10th d of each month for 1 yr.

CR1009 sown in Oct flowered in 100 d. When sown in Mar and Apr, it flowered in 130 d (Fig. 1). C14-8 sown in Nov flowered in 115 d. When sown in Dec, it flowered in 341 d, the difference being 226 d. The basic vegetative phase

1. Days to flowering of rice varieties sown in different months.

Association of rice ratooning ability and vigor with grain yield

M. Subramanian and A. Ramalingam, Agricultural Botany Department, Agricultural College and Research Institute (ACRI), Madurai, Tamil Nadu, India

We evaluated rice ratooning ability, vigor, and yield in 22 rice cultivars during 1987 wet season. The trial was laid out in a randomized block design with three replications. At harvest, the main crop was cut leaving a 15 cm culm. The stubble was irrigated 3 d after harvest and 40 kg N/ha applied 7 d after harvest.

Ratoon vigor was assessed as 1 = extra vigorous, 5 = intermediate or normal, 9 = very weak. A ratoon rating (RR) was calculated as

av number RR = (1 - [0.1 ratoon vigor]) × of ratoon

tillers/plant

IRRN 15:3 (June 1990) 9

Relationship between ratoon rating and ratoon grain yield in 22 rice cultivars. ACRI, Tamil Nadu, India, 1987 wet season.

The association between RR and ratoon yield was positive and significant (see figure). Most cultivars with high RR had high ratoon yield. RR can be used as a criterion in selecting rice cultivars for high ratooning ability.

Effect of leaf senescence and stubble carbohydrate content on ratoon rice yield S. Arumugachamy, P. Vivekanandan, and M. Subramanian, Agricultural Botany Depart- ment, Agricultural College and Research Institute, Madurai, Tamil Nadu, India

We studied the relationship between carbohydrate content in the stubble and leaf senescence at main harvest and ratoon yield in rice genotypes Bhavani, MDU3, IET6262, IET6709, IET7552, and IET9235 and their crosses during Oct 1988.

Each entry was planted in two 2-m- long rows at 20- × 10-cm spacing, in a randomized block design with three replications. Recommended practices were followed for both main and ratoon crops. Ten randomly selected plants of each parent and cross from each replication were used to estimate main crop stubble carbohydrate content, leaf senescence, and ratoon yield.

ted by phenol sulfuric acid method. Leaf senescence was estimated by

% senescent = leaves

Total carbohydrate content was estima-

Total number senescent

leaves Total number green leaves × 100

at milk stage

10 IRRN 15:3 (June 1990)

Relationship of carbohydrate content in stubble and leaf senescence at harvest to ratoon yield. a Madurai, India 1988.

Carbohydrate

stubble (%) Parent, cross content of

Bhavani 20.5 MDU3 17.8 IET6262 21.2 IET6709 23.2 IET7552 18.8 IET9239 24.2 Bhavani/MDU3 18.6 (18.2) Bhavani/IET6262 21.2 (19.4) Bhavani/IET6729 20.7 (19.7) Bhavani/IET7552 19.7 (20.9) Bhavani/IET9239 20.6 (22.0) MDU3/IET6262 17.6 (16.7) MDU3/IET6709 20.2 (21.5) MDU3/IET7552 17.8 (16.7) MDU3/IET9239 19.4 (21.2) IET6262IET6709 22.0 (23.8) IET6262/IET7552 17.5 (19.0) IET6262/IET9239 21.7 (25.2) IET6709/IET7552 20.7 (22.3) IET6709/IET9239 24.8 (23.8) IET7552/IET9239 22.6 (20.2)

Mean: Parent 20.95

SE 20.52 0.43

LSD (P = 0.05) 1.22

cross

Leaf

(%) senescence

55.2 51.4 57.6 52.9 60.8 59.6 54.0 (53.4) 54.9 (54.2) 51.2 (58.0) 66.3 (58.7) 55.0 (58.2) 52.0 (56.3) 51.4 (50.4) 5 1.7 (56.0) 56.8 (66.3) 58.4 (56.2) 62.2 (60.1) 52.9 (58.5) 56.5 (55.2) 52.5 (54.9) 62.5 (56.5) 56.26 55.71

0.94 2.65

Ratoon yield (g/10 plants)

14.4 12.3 12.8 13.6 15.1 11.7 14.5 (12.5) 16.1 (13.2) 15.4 (15.1) 14.9 (16.3) 14.3 (12.8) 12.8 (13.5) 13.1 (13.7) 12.4 (15.0) 12.5 (1 1.9) 14.4 (15.2) 13.0 (15.1) 12.8 (12.5) 15.2 (16.8) 13.5 (12.6) 15.9 (120) 13.32 13.96 0.28 0.78

Correlation with ratoon yield 0.0137 ns 0.2136 ns

a Figures in parentheses are for reciprocal cross.

IET7552 and Bhavani had the highest were not significant, indicating low ratoon yields (see table). The effects of influence of these factors on ratoon yield. carbohydrate content of the stubble and This emphasizes the importance of leaf senescence at harvest on ratoon yield inherent ratooning ability of parents.

Effect of high humidity and low temperature on spikelet fertility in indica rice

Shi Chunhai and Shen Zongtan, Agronomy Department, Zhejiang Agricultural Univer- sity, Hangzhou, China

Rains, high humidity, and low temperature lower spikelet fertility in first crop indica rice and could increase percentage of empty spikelets and reduce yields. We studied the effect of such wet weather on 12 indica varieties in 1989.

Spikelet fertility percentage (SFP) was measured on 6-10 randomly selected panicles at heading. SFP was reduced with increased humidity and decreased temperature (see figure). The most important meteorological factor was Response of 3 groups of indica varieties to relative humidity ( r = -0.96*), followed relative humidity and daily mean temperature at by mean temperature 3 d after heading. heading and flowering. Hangzhou, China, 1989.

Spikelet fertility percentage in indica varieties grown under different weather conditions. Hangzhou, China, 1989.

SFP at given heading date Degree of

Variety Normal reduction a Group b

weather Wet weather (%)

26 Jun 30 Jun 4 Jul 8 Jul Mean

88-7212 89-9382 89-9383 Cong-xie 39 Er-jiu-feng HG8547 Zhen-yu 29

Zhe-fu 802 Fu-lian-ai

Ai-gan-shan-li-qi

6713 Guang-lu-ai 4

Mean c

83.0 64.9 81.7 87.1 87.4 81.7 74.0 79.2 85.8 83.6 88.2 78.2 81.2 a

66.4 38.5 61.5 74.1 66.8 60.8 61.3 55.2 75.6 65.3 80.6 64.2 64.2 b

45.0 45.7 41.6 54.8 65.5 57.0 59.1 57.2 55.3 69.2 67.3 74.6 57.7 bc

33.0 29.7 58.9 50.4 56.4 63.5 46.3 71.2 70.1 66.6 64.9 66.0 56.4 c

48.1 38.0 54.0 59.8 62.9 60.4 55.6 61.2 67.0 67.0 70.9 68.2 59.4 bc

42.0 41.5 33.9 31.3 28.0 26.0 24.9 22.7 21.9 19.8 19.6 12.8 27.0

Susceptible Susceptible Susceptible Susceptible Middle Middle Middle Middle Middle Tolerant Tolerant Tolerant

a Degree of reduction (%) =

b SFP degree of reduction for tolerant, intermediate, and susceptible varieties was <20, 20-30, and >30, respectively. c Means followed by the same letter are not significantly different at the 5% level.

Maximum value - minimum value × 100.

Maximum value

Among varieties, SFP differed during normal weather and wet weather (see table). The varieties could be divided into three groups according to response to wet

weather. Guang-lu-ai 4, 6713, and Fulian- ai had higher SFP in wet weather than 88- 7212 and 89-9382.

Pest resistance—diseases

Some components of partial resistance to blast (BI) in indica rices

Sun Guochang, Shi De, Zhuge Gen-zhang, and Sun Shuyuan, Plant Protection Research Institute, Zhejiang Academy of Agricultural Sciences, China

Indica rice varieties Xiang-Zhou No. 5, Er-Jiu-Feng, Zhu-Ke No. 2, and Zhe-Fu 802 have shown relatively long-lasting resistance to Bl ( Pyricularia oryzae ) in farmers’ fields. In 1989, we evaluated some components of partial resistance, with Yuan-Feng-Zao as the susceptible check.

Seedlings selected for uniform growth were spray-inoculated with two pathogen isolates (10 5 conidia/ml at 20 d after sowing). The experiment was laid out in a randomized complete block design with three replications of 20 seedlings each.

Incubation period (IP, time from inoculation to first appearance of lesions),

relative infection efficiency (RE, no. of lesions/plant 7 d after inoculation [DAI]), lesion size (LS, length and width of 20 randomly selected lesions from each replication, estimated in mm 2 [lesion length × width × 0.5]), sporulation capacity (SC, total no. of conidia produced

from 5 DAI to when a lesion stopped sporulating), and difference in infectivity (DIE, percent infected plants 7 DAI) were measured. Plants were observed every 2 h beginning 70 h after inoculation. One leaf lesion on each of 10 seedlings per variety was selected and its area measured The leaf with lesion was placed in a glass tube containing 1 ml distilled water mixed with mercury bichloride, and left for 15 h.

Conidia samples were taken at 0800 h each day. Each glass tube was shaken vigorously to dislodge conidia and taken to the laboratory for counting. Conidia per lesion and per cm lesion area were calculated. Tubes with fresh solution were ins- talled on the same lesions by 1700 h daily until sporulation ceased.

The partially resistant cultivars had slightly longer IP than susceptible check Yuan-Feng-Zao (see table). RIE on Xiang- Zhou No. 5, Zhe-Fu 802, and Er-Jiu-Feng were significantly less than on the susceptible check. With isolate ZC15, RIE of all test varieties was lower, indicating it is a less aggressive isolate. LS was significantly smaller on all partially resistant cultivars than on the susceptible check.

that from the susceptible check. SC on Zhu-Ke No. 2 was the lowest for both isolates.

DIE of Xiang-Zhou No. 5, Er-Jiu-Feng, and Zhu-Fu 802 were significantly lower than that of Zhu-Ke No. 2 and the susceptible check, and were much lower with isolate ZC15 (no infection on Xiang-Zhou No. 5). This indicates that isolate ZC15

SC on all test varieties was lower than

The components of partial resistance of 5 rice varieties inoculated with isolates of P. oryzae. a

Hangzhou, China, 1989.

SC c

Variety RIE LS b IF DIE (lesions/plant) (mm 2 ) Per lesion Per cm 2 lesion (h) (%)

Xiang-Zhou No. 5 Er-Jiu-Feng Zhu-Ke No. 2 Zhe-Fu 802 Yuan-Feng-Zao

Xiang-Zhou No. 5 Er-Jiu-Feng Zhu-Ke No. 2 Zhe-Fu 802 Yuan-Feng-Zao

1.53 c 2.36 bc 3.78 ab 2.32 c 4.20 a

0.00 1.71 ab 1.94 ab 1.44 b 2.21 a

Race ZBIS (0262) 1.13 c 1.80 c 2.08 b 1.84 b 3.34 a

2,983 b 2,850 b 2,038 b 4,133 a 4,160 a

1.54 b 1.49 b 0.71 b 4.12 a

Race ZC15 (84-76)

5,267 a 2,850 b 3,000 b 5,830 a

99,667 bc 124,000 bc

70,667 c 155,500 ab 192,200 a

123,000 bc 65,667 c

146,167 ab 217,800 a

79.2 a 73.2 c 75.9 b 73.0 c 71.0 d

74.0 bc

77.5 b 83.3 a

71.6 c

46.9 b 47.1 b 81.4 a 51.1 b 95.1 a

26.5 c 45.1 b 16.9 c 84.8 a

a In each column, variety means followed by a common later are not significantly different by DMRT at P = 0.05. b Data from 7 DAI. c Mean number of conidia from samples taken 5, 7, 10, and 12 DAI.

IRRN 15:3 (June 1990) 11

--- --- --- --- ---

was less aggressive, and that Xiang-Zhou No. 5 may have specific resistance genes effective against ZC15.

The cultivars that have shown durable resistance in the field have partial resistance to the races tested in this study.

Analysis of rice blast (BI) pathogen virulence in Egypt

A. P. K. Reddy, IRRI-Egypt Project, RRTC Sakha, Kafr el Sheikh, Egypt

We evaluated the virulence of Pyricularia oryzae in B1-affected areas of the Nile Delta (governorates of Beheira, Dakhalia, Damietta, Gharbia, and Kafr el Sheikh) 1988-89 summer seasons.

Rice leaves and panicles with typical B1 lesions were collected from farmers’ fields. Single lesions were placed in petri dishes with wet filter paper and incubated at 25ºC until sporulation.

A group of conidia was aseptically transferred with a pointed capillary tube to rice leaf agar. For the purpose of this study, mass cultures from single lesions were considered equivalent to single conidial isolates. (Previous studies under the same test conditions had indicated that single conidial cultures derived from single lesions are of one race.)

In 1988, 10 commercial cultivars and 8 international differentials were tested against 35 isolates. In 1989, 8 commercial cultivars and international differentials were tested against 52 isolates.

plastic boxes in 10-cm rows, 5 cm apart were inoculated with aqueous spore

Test plants grown in 40- × 20- × 10-cm

P. oryzae isolates virulent to commercial rice cultivars in Egypt 1988 and 1989.

Virulence a (%)

1988 (n=35) 1989 (n=52) Cultivar

Giza 159 100 100 Giza 171 100 100 Giza 172 100 100 Reiho 100 100 Giza 175 3 b 2 a

Giza 181 0 0 GZ1368-5-4 0 GZ2175-5-6

nt 20 53

IR28 0 0 IR50 0 nt

a (n) = number isolates tested. nt = not tested. b Intermediate reaction.

12 IRRN 15:3 (June 1990)

suspension (about 50,000/ml). Inoculated plants were left in a moist chamber for 48 h, then transferred to the greenhouse. Disease was scored 10-15 d later.

B1 virulence on local cultivars Giza 159, Giza 171, Giza 172, and Reiho was 100% both years (see table). Virulence was zero on indica cultivars IR28, IR50, and Giza 181, and rare on Giza 175. Currently popular breeding line GZ2175- 5-6 was affected by 20% of the isolates in 1988 and 53% in 1989 (see table).

This increase in virulence on GZ2175- 5-6 is associated with an increase in area sown to this line, from 1,000 ha in 1988 to 10,000 ha in 1989.

Resistance to blast (BI) in Egyptian rice varieties

A. P. K. Reddy and A. O. Bastawisi, Rice Research and Training Centre, Sakha, Egypt

B1 is a major production constraint in Egypt. Resistance in a series of japonica varieties released in 1954-84 was short. A few indica breeding lines (IR28, IR1626- 203 [Giza 181]) released in recent years retain resistance, but they have limited commercial acceptability and narrow genetic bases.

We evaluated 500 improved cultivars, breeding lines, and germplasm of diverse origin against the prevailing B1 pathogen races ID13 and IGl in the Nile Delta.

Entries grown in the greenhouse were inoculated with two representative isolates of Pyricularia oryzae 15 d after sowing (DAS). Temperature was maintained at 21-32°C and relative humidity at >90% for 9-11 h. Cultivars found to be resistant 45 DAS are listed in Table 1.

Fifteen varieties were evaluated against three representative virulent isolates from the rice-growing delta. Entries planted in single rows in nursery boxes were inoculated at 15 DAS with virulent isolates originating from Dakhalia. Kafr el Sheikh, and Gharbia governorates. After 48 h in the humid chamber, they were transferred to glasshouse benches. Disease was recorded 15 d later.

All tested IRRI varieties were resistant to the local B1 pathogen races (Table 2). Some of the varieties (IR50, Ratna,

Table 1. Reaction of selected rice genotypes to 2 representative Pyricularia oryzae isolates of Egypt.

Reaction to P. oryzae Cultivar isolates

ID13 a IG1 b

IRRI IR20 1 1 IR22 1 1 IR24 1 2 IR28 1 1 IR36 1 1 IR50 1 1 IR52 1 1 IR60 1 1 IR62 1 1 IR64 1 1 IR66 1 1 IR2003-P18-16 1 1 IR2153-338-3 1 1 IR19743-46-1 1 1 IR25571-31-1 1 1

RD7 1 1 RD9 1 1 RD10 1 1 RD2l 1 1 RD25 1 1

Iri 370 1 1

Milyang24 2 1 Milyang 80 2 1 Milyang 85 2 1 Suweon 346 1 1

BL 1 1 1 Kanto 1 1 2 Tsuyuake 1 3 Toride 1 1 1

Bala 1 1 Basmati 370 1 1 Cauvery 1 1 CO 43 1 1 Padma 2 4 Ratna 1 1 Rasi 1 1 Tella hamsa 1 1

Mars 1 1 Lemont 1 1 Mercury 1 1 Noritai 1 1

Agami 3 4 Giza 175 2 1 Giza 181 1 1

Yabani 15 7 8

Giza 159 (susceptible) 8 8 Giza 172 (susceptible) 8 8 Reiho (susceptible) 8 8

Thailand

S. Korea

Milyang 23 2 1

Japan

India

USA

Egypt

Giza2175-5-6 8 2

(susceptible)

a Isolate from Sidisalem, on Giza on 2175-5-6. b Isolate from RRTC research farm Sakha, on Giza 172.

Cauvery) have a history of susceptibility in the tropics. IR36, Rasi, and a few

Table 2. Reaction pattern of 15 rice varieties to 3 Pyricularia oryzae isolates in Egypt.

Reaction to isolate Reaction Variety

Po 361 a Po 359 Po GMI Mean

Egypt Phil/India

Indica Cauvery 2.0 Ratna 1.0 IR50 1.0 IR36 1.0 IR28 1.0 Giza 181 1.0 Rasi 1.0

Gz 159 8.0 Gz 171 6.5 Gz 172 8.0 Reiho 7.5 Shin 2 5.5 Aichi Asahi 8.0 Kanto 51 1.0 Toride 1 1.0

Mean 3.5

CV (1) 7.1 CV (2) 6.0 LSD Main plot at 0.05

Interaction LSD at 0.05 0.01

Japonica

Isolates at 0.01

1.0 1.0 1.3 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0

9.0 9.0 8.6 9.0 9.0 8.2 9.0 9.0 8.6 9.0 9.0 8.5 6.5 6.0 6.0 9.0 9.0 8.6 2.0 1.0 1.3 1.5 1.0 1.1 4.1 4.0

Subplot LSD (0.05) = .27 (Varieties) (0.01) = .36

= 0.47 = 0.64

R R R R R R R

S S S S MS S R R

S S S MR MS S R

S S S S S S S R

a Average value of 2 replications. Po 361 from Kafr El-Sheikh governorate, Po 359 from Dakhalia governorate. Po GMI from Gharbia governorate

others that have shown more durable ments appear to be better donors of B1 resistance in other rice-growing environ- resistance in Egypt.

Changes in rice leaf pigment releasing three viruliferous Nephotettix due to tungro (RTV) infection virescens (Dist.) per seedling. Infected

leaves were graded as 1/3 orange yellow, B. Srinivasulu and R. Jeyarajan,Plant 2/3 orange yellow, or completely orange Pathology Department, Tamil Nadu Agricul- yellow. Chlorophyll content was extracted tural University, Coimbatore, India and estimated in 80% acetone. Carotene

and xanthophyll were extracted with 95% Chlorosis and orange yellow color in ethanol and 85% methanol, respectively, leaves are characteristic symptoms of and estimated colorimetrically. RTV disease in rice. We investigated the Chlorophyll content of diseased leaves effect of RTV infection on green pigment was reduced in proportion to the length of (chlorophyll), orange pigment (carotene), orange-yellow color on a leaf (see table). and yellow pigment (xanthophyll) at In leaves that had turned completely different stages of pathogenesis. orange yellow, chlorophyll a, chlorophyll

Fifteen-day-old seedlings of suscep- b , and total chlorophyll were reduced by tible TN1 were inoculated with RTV by 90, 94, and 91%, respectively.

Effect of RTV on pigment of rice leaves. Coimbatore, India.

Leaf color Chlorophyll a Chlorophyll b Total Carotene Xanthophyll chlorophyll

Completely orange yellow 0.234 0.078 0.3 12 ND* ND 2/3 orange yellow 0.564 0.1 19 0.689 0.005 0.003 1/3 orange yellow 1.380 0.680 2.184 ND ND Healthy 2.300 1.370 3.672 0.003 0.002

LSD (P = 0.05) 0.26 0.110 0.190

a ND = not determined

A slight increase in carotene and xanthophyll content was found in diseased leaves.

Development of kresek symptoms on some rice varieties

Y. Suryadi, Plant Pathology Department, Sukamandi Research Institute for Food Crops, Subang 41256, West Java, Indonesia

Xanthomonas campestris pv. oryzae (Xco) can cause kresek symptoms on rice seedlings. Great variations have been found among strains of Xco in terms of their pathogenicity in the rice plant.

using different strains of Xco on seven rice varieties. The experiment was laid out in a split-plot design with two replications, with rice varieties Pelita 1-1, Java 14, Gemar, Cisadane, Citanduy, TNl, and IR54 in the main plots and three isolates or strains of Xco in the subplots.

Roots of 21-d-old seedlings were washed, dip-inoculated for 15 min with 48-h-old bacterial suspension (±10 9 cfu/ ml), and seedlings transplanted in a wooden seedling box. Disease incidence was recorded 14 d after inoculation.

Symptom development varied (see table). Cisadane had the least disease symptoms with all three Xco strains, followed by Java 14, Pelita 1-1, and Gemar. Mean infection ranged from 9.7 to 44.3%.

We induced kresek in the screenhouse

Development of kresek symptoms on 7 rice varieties Sukamandi, Indonesia, 1988.

Wilted plant a (%) Variety

Si 8502 Si 8401 Si 8519 Mean

Gemar 16.55 12.68 17.83 15.67 ab Cisadane 9.26 11.93 7.97 9.72 a Citanduy 26.75 21.65 20.72 23.04 bc Pelita 1-1 14.56 19.94 11.95 15.48 ab IR54 36.99 33.85 22.62 31.15 c Java 14 14.31 16.06 16.05 15.47 ab TN1 51.09 48.74 32.94 44.26 d

Mean 24.21 a 23.55 a 18.58 b -

CV variety (%) = 33.28 CV isolates (%) = 17.73

a Isolates Si 85012, Si 8401,and Si 8519 represented Indonesia bacterium groups III, V, and VI, respectively. Means followed by the same letter do not differ significantly by DMRT (P = 0.05).

IRRN 15:3 (June 1990) 13

Resistance of wild rices to bacterial blight (BB)

R. Ikeda and G. A. Busto, Jr., Plant Breeding Department, IRRI; and T. Ogawa, National Agriculture Research Center, Tsukuba, Ibaraki 305, Japan

We evaluated 198 wild rice accessions-10 wild species and 22 natural hybrids against six races of BB caused by Xanthomonas campestris pv. oryzae Feb- May 1989 in the screenhouse at IRRI.

Reactions to the BB races were tested using the clipping method. Five seedlings/ pot per accession were inoculated at booting to heading stages. Lesion length was measured 18 d after inoculation, resistance was lesion length less than 10 cm, susceptibility was lesion length longer than 20 cm.

More than half the tested accessions showed resistance to all six races (Table l). (Only a few cases of resistance to all six races in the Philippines are known in O. sativa varieties.)

Based on patterns of reaction to the six races in each accession, 18 are suspected to have the Xa-3 gene, 11 the xa-5 gene, 2 the Xa-10 gene, and 4 the Xa-14 gene (Table 2). The Xa-4 gene, one of most popular resistance genes in O. sativa varieties of tropical Asia, was not found.

Table 1. Best resistance to 6 BB races found in 198 accessions of wild species. IRRI, Feb-May 1989.

IRGC Lesion length (cm) Species accession Origin

no. 1 2 3 4 5 6

O. rufipogon O. rufipogon O. rufipogon O. rufipogon O. nivara O. officinalis O. officinalis O. officinalis O. officinalis O. eichingeri

104647 104829 104830 104851 104705 105081 105120 105121 105174 105160

Thailand Thailand Thailand Thailand India Myanmar Philippines Philippines Malaysia Uganda

1 1 1 1 1 1 1 1 1 1

1 1 1 1 1 1 1 1 1 1

1 1 1 1 1 1 1 1 2 1

1 1 1 1 1 1 1 1 1 1

1 1 1 1 1 1 1 1 1 2

1 1 1 2 2 2 1 2 1 1

Table 2. Distribution of BB resistance genes in 198 accessions of wild species. IRRI, Feb-May 1989.

Genome Species tested Accessions Occurrence (no.) of suspected gene

(no.) RRRRRR a Xa-3 xa-5 Xa-10 Xa-14

AA O. rufipogon 98 66 9 O. nivara 20 4 2 1 2 1

22 Natural hybrids 8 2 3 A g A g O. barthii 2 A 1 A 1 O. longistaminata 2 1 A g1 A g1 O. glumaepatula 1 CC O. officinalis 32 16 3 8

O. rhizomatis 4 3 1 O. eichingeri 3 3

CCDD O. latifolia 11 5 2 O. grandiglumis 3 1

a RRRRRR indicates resistance reactions to six Philippine races of BB.

Pest resistance–insects Biology of rice leaffolders (LF) on susceptible IR36 and resistant TKM6

M. L. P. Abenes and Z. R. Khan, ICIPE-IRRI Project, IRRI

IR36 is normally used as the susceptible check and TKM6 as the resistant check for rice LF Cnaphalocrocis medinalis (Guenée). We reared 200 LF from the first-instar larval stage to pupation in individual cages, on 30- to 35-d-old IR36 and TKM6 plants under standard greenhouse conditions.

Larvae that pupated were weighed individually. A growth index was calculated as the percentage of larvae pupating divided by the average larval period on each host.

14 IRRN 15:3 (June 1990)

Pupae were incubated and the first 20 pairs of moths emerging from each host were kept in cages for mating. Adult longevity of males and females was observed separately. Fecundity was measured as number of eggs laid by each female.

Larval survival, growth index, and pupal weight on susceptible IR36 were

significantly higher than on resistant TKM6 (see table). In the first 20 pairs of moths emerging from the hosts, adult longevity on TKM6 was not significantly different from that on IR36. On the average, female moths laid the same number of eggs. In a follow up study, adult LF emergence was 55% on IR36 and 31% on TKM6.

Biology of C. medinalis raised on susceptible IR36 and resistant TKM6. a

Larvae Growth Growth Pupal Adult longevity (d) Fecundity Variety becoming period index weight (eggs/female)

pupae (%) (d) (mg) Female Male

IR36 93 18.2 5.1 21.4 7.5 8.2 TKM6 81

86.6 19.1 4.2 17.9 9.0 8.6 99.6

Diff. 12** -0.9** 0.9** 3.5** -1.5 ns 4.4 ns -12.8 ns

*ns = not significant; ** = significant at P < 0.01 level by t test.

Rearing yellow stem borer (YSB) for screening varietal resistance

R. C. Saxena, F. G. Medrano, and L. M. Sunio, Entomology Department, IRRI

YSB Scirpophaga incertulas (Walker) moths lay eggs on rice plant leaves. Shortly after hatching, the neonate larvae bore into the plant tissues. Larval feeding at the vegetative and reproductive stages causes deadhearts (DH) and whiteheads.

Many cultivars are susceptible to YSB, and even moderate host plant resistance is

Steps in rearing YSB for resistance studies.

highly desirable. We developed a procedure to rear stem borers year-round, to help speed screening for varietal resistance.

resistant to other insect and tungro viruses) are transplanted weekly in 34- × 25- × 11-cm plastic trays (see figure). At mid-booting, a 2.5-cm-long slit is made with a scalpel in the bulging middle portion of the leaf sheath below the flag leaf. The incision is dilated to expose a small portion of the developing panicle. One to two first-instar YSB larvae are released onto the panicle and the incision closed.

Seedlings of IR62 (susceptible to YSB,

At 25-30 d after infestation (DI), when larvae have pupated, plants are cut 15 cm above the base. The trays with stubbles are transferred to a 2- × 1- × 1-m screen cage for adult emergence. About 80% of the infested tillers produce moths.

Emerging moths are collected daily and transferred to oviposition cages with

with egg masses are removed from those plants two times a week and placed in 15- × 1.5-cm test tubes or small ball jars.

At 27 ± 2 °C, eggs hatch in about a week. Emerging larvae are used for varietal screening, for basic studies, or for maintaining the insect culture.

potted 40-d-old TN1 plants. Leaf cuts

MDU3, a new gall midge- resistant rice

S. Jebaraj, G. Soundarapandian, M. Subramanian, M. S. Venugopal, and G. Logeswaran, Agricultural College and Research Institute, Madurai 625104, Tamil Nadu, India

Our breeding work for gall midge (GM) Orseolia oryzae Wood Mason resistance identified a superior rice culture ACM8. In screenhouse and field tests in the endemic area, ACM8 yielded higher than highly susceptible IR20. ACM8 has been released as MDU3 exclusively for the GM endemic area.

MDU3 (IET6012) is a derivative of a cross involving IR8 and Warangal 1263. Grain yields in experiment station trials averaged 4.7 t/ha, 22.4% higher than IR20 (Table 1). In adaptive farmers’ field trials at 24 locations, ACM8 yields averaged 4.9 t/ha, 10.9% higher than IR20. In na-

Table 1. Overall performance of MDUJ and IR20 in Tamil Nadu, India.

Trial Increase

MDU3 IR20 over IR20 (%)

Grain yield (t/ha) Research station 4.7 3.8 22.4

Adaptive research 4.9 4.4 10.9

AICRIP trial c 4.1 3.8 7.9

trials a

trials b

Productivity/d (kg/ha) 41.4 30.9 13.7

a Mean of 6 yr. b Mean of 24 locations. c Mean of 7 centers.

IRRN 15:3 (June 1990) 15

tional yield trials at seven locations throughout India, performance was encouraging. Overall performance indicates yields 13.7% higher than IR20.

ability and is nonlodging. It matures in 120-125 d, 5-10 d earlier than IR20, and has high productivity per day. The grain is long and slender with white rice; cooking

ACM8 was screened under artificial as

MDU3 is semidwarf with high tillering

quality is good.

well as field conditions for the important pests and diseases (Table 2). It is highly resistant to GM; resistant to brown planthopper (BPH), leaffolder, and blast and moderately resistant to whitebacked planthopper (WBPH) and brown leaf spot.

Table 2. Reaction to major insect pests and diseases at Madurai, Tamil Nadu, India.

Pest Score a

ACM8 IR20 (MDU3)

BPH (screenhouse) 3 7 WBPH (screenhouse) 5 7 Gall midge

Screenhouse 0 7 Field 0 9

Leaffolder 3 7 Blast (field)

Leaf 3 3 Neck 3 5

Brown leaf spot (field) 5 3 Sheath rot (field) 3 3

a By the Standard evaluation system for rice.

Using rice nurseries to collect thrips for use in screening rice germplasm

R. Velusamy, Tamil Nadu Agricultural University (TNAU), India; and R. C. Saxena, IRRI

Breeding for resistance to thrips Stenchaetothrips biformis (Bagnall) has lagged because of the lack of large pest numbers needed for screening germplasm.

Greenhouse cultures have failed to provide the thousands of thrips needed.

We developed a simple technique to collect thrips directly from rice nurseries. The nurseries are sown every 2 wk during peak thrips incidence.

Pregerminated IR64 seed was sown in 7- × 1-m beds Aug-Oct 1988 in Coimba- tore. At 10, 20, and 30 d after sowing (DAS), seedlings were examined under a binocular microscope. Thrips population/ seedling was 5-6 adults at 10 DAS, 60-70

Schematic of procedure for collecting rice thrips from nurseries to use in screening rice germplasm for thrips resistance.

16 IRRN 15:3 (June 1990)

nymphs at 20 DAS, and 75-80 adults at 30 DAS . Thrips nymphs were mopped up at 20 DAS by passing a wet palm 4-5 times across seedlings in the nursery and freed by dipping the hand in a pail of water (see figure). We collected 200-250 thrips per sweep.

Water containing thrips collected per 25 sweeps was poured uniformly on 7-d- old seedlings of test cultivars (including resistant Ptb 21 and susceptible TN1) grown in wooden trays (60 × 40 × 10 cm) inside a large water-filled iron tray. Each seedling was infested with 5-6 nymphs.

Alternatively, water containing thrips was poured on 30-d-old TN1 plants kept inside a water-filled tray. Nymphs settled readily on TN1 plants, which were then tapped gently over seedling trays for infestation. Using thrips collected this way, we were able to screen 400 entries for resistance. The technique can be used in areas where dry weather prevails for 3- 4 mo. Thrips populations peak with the onset of dry weather; heavy rains wash them away.

Pest resistance- other pests

Reaction of rice cultivar Faro 11 to sugarcane cyst nematode Heterodera sacchari

O. A. Fademi, Rice Research Programme, NationaI Cereals Research Institute, Badeggi, P.M.B. 8, Bida, Niger State, Nigeria

H. sacchari (Luc and Merny) is wide- spread in sugarcane cropping areas of Nigeria. In many of the mid-belt states of Nigeria, rice and sugarcane are intercropped or relay-cropped. In earlier screening of some rice varieties, all were susceptible to H. sacchari. We studied H. sacchari pathogenicity on rice.

Ten-liter plastic buckets were filled with soil collected from an H. sacchari- endemic field at the Nigerian Sugar Company plantation, Bacita, and planted with rice cultivar Faro 11. Inocula were juveniles emerging from cysts collected earlier from the same field using a

Effect on rice of H. sacchari at various inoculum levels. a Niger State, Nigeria

Inoculum level Panicle (nematodes/ Tiller no. exsertion

plant) (cm)

0 6.55 a 10.50 c

1,000 4.56 c 12.55 ab

5,000 4.25 c 13.28 a 10,000 5.09 b 11.63 bc

a Mean separation by DMRT.

Fenwick can and incubated in petri dishes. Inocula were applied at 1,000,

soil was the control treatment. The experiment was laid out in a completely randomized block design with four replications.

Both tillering and panicle exsertion were affected significantly by increasing levels of H. sacchari (see table). Above the 5,000 inoculum level, nematode influence was less pronounced. This may be related to the self-regulatory property of H. sacchari populations under limited food supplies: some juveniles die while others undergo sex change into nonpara- sitic male forms.

5,000, and 10,000/plant. Steam-sterilized

Stress tolerance– adverse temperature

Promising cold-tolerant and high-yielding rice lines for Ndop Plain, Northwest Cameroon

M. P. Jones, S. B. C. Wanki, A. C. Roy, and J. A. Ayuk-Takem, IRA/NCRE/USAID/IITA Rice Project, Dschang, Cameroon, and UNVDA, Ndop, Northwest Province, Cameroon

Rice in Cameroon grows over a broad range of climatic conditions, from a dry tropical climate with less than 800 mm rain in the north to a humid tropical climate with more than 2,000 mm rain in the northwest and west. At Ndop Plain (1,200 m above sea level) in the northwest, about 3,000 ha is planted to irrigated rice with a potential for 15,000 ha.

The rice crop is exposed to low temperature (13-20°C) and associated disease problems (sheath rot [ShR] and glume discoloration [G1D]). Low air and water temperatures, low light intensity, high relative humidity, and intermittent strong winds are yield constraints.

Agronomic studies have shown that changing the planting time is an alternative to escape low temperatures during critical late vegetative and early flowering phases. However, the present area is cultivated by more than 6,000 small farmers, with limited ability to adopt this practice.

Varieties that fit a longer range of planting times are needed. IR7167-33-2-3 was released in 1986 to replace Tainan 5. Its medium, bold, and fairly chalky grain type was an improvement over the short, bold, and chalky grains of Tainan 5. IR7167-33-2-3 and Tainan 5 yield an average 3.5 and 3.0 t/ha under farmers' management. The need is for suitable high-yielding varieties with long, slender, translucent grain.

Two advanced lines, TOX3344-TOC- 3-4 (derived from TOX3117-18-1/ ITA212) and TOX3145-TOC-34-2-3

(from ITA212/B2161C-MR-57-1-3-1), have been identifed as promising. Their overall performance over 3 yr (1986-88) in on-station trials at Bamunka, Ndop Plain, was good. Grain yields averaged 6.3 and 5.8 t/ha (Table 1). In researcher- managed trials at Dschang (alt. 1,400 m) during 1988, TOX3344-TOC-34 and TOX3145-TOC-34-2-3 yielded 5.5 and 4.6 t/ha, respectively. Highest yields so far were 7.1 t/ha for TOX3344-TOC-34 and 6.3 t/ha for TOX3145-TOC-34-2-3.

TOX3145-T6C-34-2-3 and TOX3344-TOC-3-4 show greater tolerance for low temperature and greater resistance to ShR and G1D (Table 2). Panicle tip degeneration was more severe in IR7167-33-2-3 and Tainan 5; this is believed to cause direct yield losses.

TOC-34-2-3 have long, slender, translucent grains and, when cooked, are flaky, a characteristic preferred by farmers and local consumers. Palatability tests in 1988 placed TOX3344-TOC-3-4 as best in cooking quality and taste. It is a candidate for release for general cultivation at Ndop Plain.

TOX3344-TOC-3-4 and TOX3145-

Table 1. Characteristics of promising varieties or advanced lines for irrigated conditions at Ndop Plain, Northwest Cameroon.

Cultivar Grain Plant Growth Yield b

type a height duration (t/ha) (cm) (d)

TOX3344-TOC-3-4 L/S 90 120 6.3 TOX3145-TOC-34-2-3 L/S 83 120 5.8 IR7167-33-2-3 c M/B 100 110 4.6 Tainan 5 c S/B 95 111 3.8

a L/S = long and slender, M/B = medium and bold, S/B = short and bold. b Yields averaged over 8 on-station trials 1986-88. c Currently recommended variety.

Table 2. Reaction of promising varieties or advanced lines to low temperature and associated diseases at Ndop Plain, Northwest Cameroon.

Low temperature a Disease score a

Cultivar Visual score Panicle tip ShR GlD 4 WT degeneration (0-9) 2 WF (%)

TOX3344-3-4 3 5 1 1 TOX3145-TOC-34-2-3 3 5 3 3 IR7167-33-2-3 b 5 10 3/5 3 Tainan 5 b 1 20 3/5 5 a WT = weeks after transplanting. WF = weeks after flowering. b Currently recommended varieties. Scored with the Standard evaluation system for rice.

IRRN 15:3 (June 1990) 17

Performance of cold-tolerant varieties in western hills of Nepal

B. R. Sthapit, Crop Science Section, Lumle Agricultural Centre, P.O. Box No. 1, Pokhara, Kaski, Nepal

A large portion of rice in Nepal is grown at 1000-2000 m above sea level, where low temperatures cause cold damage. Most varieties grown in high altitudes are indigenous. We evaluated 28 genotypes in 1989 at our Chhomro off-station research site (2000 m above sea level). They were indigenous varieties Raksali, Palung 2, and Chhomro local and materials obtained from IRRI, and the Nepal Rice Improvement Program, Parwanipur, and Botany Division, Khumaltar.

Water temperature during anthesis (Oct-Nov) was 20.2 °C; mean minimum temperatures were 15.1-16.5 °C; mean maximum, 16.3-19.7 °C. During early seedling growth (Jun-Jul), minimum temperatures were 14.5-16.4 °C and maximum temperatures, 21.9-23.1 °C.

Agronomic traits for cold tolerance were good in some exotic varieties (see table). Spikelet sterility was 100% in all genotypes except Chhomro local (14%) and Seto Bhakunde (25%). Those local varieties produced some yield.

Internationally known cold-tolerant

Screening rice for temperature tolerance in northern Nigeria

W. N. Umeh, National Cereals Research Institute, P.M.B. 1022, Birnin Kebbi, Sokoto State, Nigeria

Most rice production in Nigeria is restric- ted to the wet season, with a long fallow between seasons. Irrigation schemes in the northern states provide an opportu- nity to overcome contingent drought and increase rice production through better land utilization.

Development of temperature-tolerant rice varieties would help reduce the long fallow in areas with 3-4 mo of cold weather (Nov-Jan/Feb) and 3-4 mo hot weather (Feb-May).

18 IRRN 15:3 (June 1990)

Some agronomic traits a of selected cold-tolerant rice genotypes at Chhomro (altitude 2000 m), Nepal, 1989.

Plant Tillering Cold Panicle Genotype

Sheath vigor ability tolerance exsertion rot

(1-9 scale) (1-9 scale) (1-9 scale) (1-9 scale) (1-9 scale)

Akiyudaka 7 9 5 5 3 Chhomro Local (check) 3 5 5 1 1 Fuji-102 9 9 7 5 3 IRI-353 3 5 3 5 3 K335 9 9 7 5 3

Palung 2 7 7 9 5 5 Rakshali 5 5 5 5 3 Rodina 9 9 7 5 5 Stejaree 45 9 9 5 3 3 Bhutan 11 9 9 5 3 3

NR10157-2B-17-2 9 9 9 5 7

B4190E-CW-139-29-176 7 5 9 5 3 B4448E-35R-1 7 7 9 5 3 Cheonmabyeo 9 7 7 3 3 Chhomro (check) 5 3 5 1 1 IR15579-166 7 7 9 5 3 IR23325-R-R-B-7-2-2 5 5 9 3 3 IR26036-2-2-2-3 7 7 7 5 7 Ml0l 7 5 5 3 3 NR10157-2B-13-1 7 7 7 5 3 NR10157-2B-13-5 5 5 1 5 5 NR10157-2B-17-1 9 5 7 5 7 NR10167-2B-7 3 5 7 5 3 NR10164-2B-14 7 3 9 5 7 NR10167-2B-16 7 7 9 5 7 NR10177-B-11 7 5 9 5 3 NR10180-B-13-3 7 5 7 5 7 NR10180-B-13-4 7 7 7 5 5 Seto Bhakunde 3 5 5 1 3

a By Standard evaluation system for rice scale. Only Chhomro Local, Chhomro, and Seto Bhakunde gave some yield.

materials such as China 1039, Akiyudaka, indigenous varieties from the Himalayan and Stejaree 45 failed to set grain. belt for use in the breeding program for

This suggests a need to evaluate more cold-tolerant rices.

The cold season is characterized by no (Harmattan is the northeasterly cold wind rainfall, high and frequent cold harmattan that blows from Europe, across the Medi- wind. low minimum but relatively high terranean and Sahara desert, and down the maximum temperature, low relative coast of West Africa.) humi-dity, hazy and dusty atmosphere, Atmospheric demand for moisture (in- and high evapotranspiration (Table 1). dicated by piche evaporation) is high from

Table 1. Climatological data for cold and bot months. a Northern Nigeria, 1988.

Month Rainfall Wind speed Piche evaporation Temperature (°C)

(mm) Maximum Minimum (kg/h) (ml/d)

October November December January February March April May

0 0 0 0 0 0 5.8

Trace

36 35 30.4 30.9 34.3 38.8 40.0 40.3

23 20 17.3 17.6 19.7 26.0 28.2 29.3

158.40 188.22 245.47 294.92 283.20 261.55 243.1 250.2

14.5 19.5 21.9 23.9 26.6 29.7 21.6 19.8

a Courtesy of the Meteorological Department, Sokoto Station, Nigeria.

Nov to May compared with Jul-Sep. Irri- gation water, air, and soil surfaces are cold. (This also affects labor productivity.)

We screened 100 rice lines for cold tolerance in 1987-88. Lines were seeded 18 Dec 1987. Eight failed to germinate. Seedlings in the nursery exhibited stunted growth, leaf yellowing, scorched leaf tips, retarded tillering, and poor root development.

Seedlings were transplanted 18 Feb 1988 in nonreplicated 4- × 6-m micro- plots. Average plant height at transplanting was 6 cm. Twenty entries died after

Irrigation was from tubewells, and was maintained at 13-15 cm depth. As general weather conditions improved toward the end of Feb, seedlings became more vigorous.

Eight entries had 100% empty glumes; incidence of sterility in the remaining 64 entries ranged from 18 to 60%. This may be attributed to high temperature and high winds at anthesis in late Mar to early Apr.

Plant height at maturity ranged from 69.4 to 95.0 cm; days to 50% flowering ranged from 105 to 142 (Table 2).

The best 18 entries were selected for further advanced yield trials 1988-89.

transplanting.

Table 2. Growth characteristics and grain yield of

88. cultivars selected for cold tolerance. a Nigeria, 1987-

Days to Plant Grain yield Cultivar a 50% height g/pot

flowering (cm) (2.4m 2 )

RNR74229 122 83.3 1380 RTN76-2-1-1-1 127 90.4 1300 IR13538-48-2-3-2 115 79.2 1230 IR27325063-2-2 122 84.4 1180 BR161-23-59 122 75.2 1180 FAROX233-1-1-3 127 82.2 1160 C1321-2 122 72.4 1140 IR24594-272-2-2 121 95.0 1120 KUA1727 127 90.6 1120 BG367-4 105 84.4 1100 IR28210-68-4-1-3 109 80.2 1100 IR28118-138-2-3 142 90.4 1100 ITA302 122 83.4 1080 lTA121 111 69.4 1060 C1158-7 138 77.4 1040 16439 116 74.4 1040 BG276-5 105 80.0 1000 ET6279 122 80.2 1000

a Cold tolerance score for these entries is 5 by the Standard evaluation system for rice.

Stress tolerance–adverse soils Phosphorus activity in correlation coefficients were estimated, genotypes with low and path analysis done. phosphorus tolerance P content in leaf at 60 d showed a

significant negative correlation ( r g = -0.413) with sound grain P (see table); N. D. Majumder (Present address: Central

Agricultural Research Institute, Port Blair other correlations were not significant 744101, India), S. C. Rakshit, and D. N. Root P had a significant, positive Borthakur, ICAR Research Complex, Shillong association with P content in stem ( r p = 793004, India 0.603, r g = 0.722). leaf ( r p = 0.419, r g =

0.507), and sound grain ( r p = 0.525, r g = Seven P-tolerant varieties (IR28, IR29, IR30, Khonorullo, Mirikrak, Pawnbuh, and Ngoba) and their 21 cross combinations made in a diallel fashion without reciprocals were sown in upland lateritic soil deficient in P (5 ppm available P, pH 5.0). The experiment was laid out in a randomized block design with three replications. Spacing was 20 cm between plants and between rows.

Plant tissue analysis was done 60 d after seeding (leaf) and at harvest (root, leaf, stem, panicle without grain, and sound grain). Genotypic and phenotypic

0.588) at both the phenotypic and genotypic levels. A significant, positive association was found between P content in stem and leaf at harvest; that between grain yield and plant was significant and negative at phenotypic and genotypic levels.

The effect of P activity through different pathways and its role in yield was determined using genotypic and phenotypic correlation coefficients. The genotypic correlation had a higher magnitude. The highest direct positive contribution was made by P in the root

Phenotypic and genotypic correlation a coefficients of P content in leaf at 60 d growth, different organs at harvest, and grain yield per plant and direct contributions to yield.

Correlation coefficients of P content b

At 60 Direct d growth At harvest effect

Leaf Root Stem Leaf Panicle Grain without

(1) (2) (3) (4) (5) (6)

(1) 0.230 0.280

grain

(2) r p -0.093 r g

-0.112

(3) r p 0.044 0.603** r g

0.070 0.722**

(4) r p 0.184 0.4 19* 0.634** r g

0.185 0.507** 0.726**

(5) r p -0.292 0.057 0.062 0.260

r g -0.347 0.075 0.065 0.288

(6) r p -0.353 0.525** 0.332 0.292 0.237 r g

-0.413* 0.588** 0.359 0.303 0.241

0.21 1 0337

0.051 0.080

-0514 -0.669

0.028 0.038

-0.080 -0.135

(7) r p c 0.154 -0.039 -0.166 -0.382* -0.232 -0.190 - r g c 0.167 -0.052 -0.189 -0.418* -0.255 -0.217

a r p , r g phenotypic and genotypic correlation coefficients. b Significant at 5% (*) and 1% (**) levels. c For grain yield/plant.

IRRN 15:3 (June 1990) 19

-

Manoharsali as checks were field tested at research stations and in field trials in Gerua, Tinsukia, and Suklivoria for 1-6 yr. Trials were laid out at 20- × 15-cm spacing with 2-3 seedlings/hill. Forty kg N as urea was applied in three splits before planting, at tillering, and at panicle initiation; 20 kg/ha each of P and K were applied in the form of single superphosphate and muriate of potash as basal.

IET6666 showed wide adaptability and stability in grain yield under the agroecological conditions of Assam (Table 2). It flowered in 115-120 d and matured in 145-157 d.

The variety is being evaluated for release as Lakhimi for Assam wet season.

(0.337) at harvest, followed by P in leaf at 60 d and in stem at harvest. The indirect effects of P in stem, grain, leaf, and sterile panicles via root were all

positive. An indirect positive effect was found via stem at harvest. The direct and indirect contributions of leaf and sound grain were negative.

IET6666, a new high-yielding rice variety for Assam

K. Chandra, D. K. Barua, U. Kalita, D. Dutta, and B. Bharali, Assam Agricultural University, Regional Agricultural Research Station, Titabar 785630 (Assam), India

IET6666, a long-duration, high-yielding variety evolved from RP31-49-2/Patnai

23 by the Directorate of Rice Research in Hyderabad, is suitable for low-lying fields and cloudy weather conditions during wet season. Its coarse grain and intermediate plant height are preferred by the majority of farmers in Assam.

Agronomic characteristics are given in Table 1.

IET6666, 12 other promising cultivars with similar duration, and Mahsuri and

Integrated germplasm improvement

Table 1. Morphological and physiological characteristics of IET6666 and check variety Manohar- sali at Titabar, Assam, India.

Character IET6666 Manoharsali

Plant height (cm) 118.73 148.53 Duration 145 148 Panicles (no./m 2 ) 257 242 Filled grains (no./ 103 83

panicle) 1000-grain weight (g) 23.22 24.55

flowering (kg/ha) Total dry matter at 116.76 146.56

Leaf area index 4.58 5.80 Total chlorophyll 2.23 3.43 content at flowering (mg/g fresh wt)

at flowering (%)

efficiency for dry matter (%)

for grain yield (%)

N content in leaf tissues 2.1 8 1.23

Solar energy utilization 1.87 0.81

Solar energy utilization 0.55 0.25

Table 2. Yields of IET6666 and check varieties at different locations in Assam, India 1978-88.

Yield (t/ha)

Year Location IET6666 Mahsuri

1978 Titabar 3.4 2.7 Karimganj 3.0 3.3





1984 Titabar 5.3 3.1 1985 Titabar 5.3 3.2 1986 Titabar 5.2 3.2 1987 Titabar 5.4 3.2 1988 Titabar 5.1 2.6 1984 on-farm trials Gerua 6.4 5.2

Tinsukia 5.1 4.2 Suklivoria 3.9 4.0

Performance of IR46 and lR10781-143-2-3 under transplanted rainfed lowland conditions in Nepal

G. L. Shrestha and A. C. Shrivastava, National Rice Improvement Program (NRIP), Parwanipur Agriculture Station, Birganj, Nepal

In Nepal, 88% of the rice area (1.45 million ha in 1988) is in the subtropical climatic region of the Tarai belt (67-250 m altitude), the Inner Tarai region, and equivalent climatic region of river basin areas and valleys up to 900 m altitude.

20 IRRN 15:3 (June 1990)

Table 1. Yields of IR46 and IR10781-143-2-3 at 4 sites in subtropical Nepal, 1983-86.

Yield (t/ha) Increase Variety over Experiment site a

Tarahara Parwanipur Rampur Nepalganj Mean check(%) and time

IR46 Improved check

IR46 Improved check

Masuli IR10781 Improved check

IR10781 Bindeshori

Improved check Masuli

Bindeshori

4.6 2.6 3.0 2.4 2.2 2.0

4.8 2.6 2.4 3.3 2.0

3918 2956 2692 3 562 3001 2512

4840 2818 3750 3292 2012

3 2 2.8

4.2 a

3.9

2981 2897

4150 3900

3.4 142 2.4 100

3.5 114 3.1 100

3.1 105 3.0 100

3.9 127 3.1 100

Research stations, 1983-84

Farmers' fields, 1985-86

Research stations, 1984-85

Famers' fields, 1985-86

a Farmer's field result of this location is from Nawal Parasi area. Each location includes the results from various farmers' fields.

Manoharsali

-

-

- - - - - - - - - - - -

- - - - - -

Under assured irrigation, two crops of rice are grown during the summer (Feb- Jun) and rainy (Jun-Oct) seasons, with a nonrice winter crop grown Nov-Jan.

More than 75% of the country's ricefields are rainfed, dependent on the monsoon. We are trying to identify high- yielding rice varieties suitable for transplanted rainfed lowland conditions.

IR46 and IR10781-143-2-3 have shown consistently better performance over recommended check Bindeshori and popular improved variety Masuli (Mahsuri) in trials for the last 5 yr (Table 1). Yields have averaged more than 3.0 t/

Seed technology Using electrical conductivity to determine maturity stage for quality rice seeds K. Sivasubramanian and T. V. Karivara- tharaju, Tamil Nadu Agricultural University, National Pulses Research Centre, Vamban 622303, India

We studied the influence of maturity stage on the keeping quality of seeds.

harvested at 27, 34, and 41 d after 50% anthesis. Seeds were dried to 8% moisture content, treated with captan (N- trichloro methyl thio)-Cyclohex-4-ene- 1,2-dicarboximide), and stored in cotton and paper-aluminum foil-polythene laminated (P-AF-P) containers for 9 mo.

Electrical conductivity of the seed leachate was measured at 3-mo intervals using Elico CM-82 Conductivity bridge.

Leachate was prepared using 50 randomly selected seeds, soaked in 50 ml of deionized water for 24 h at room temperature, with two replications.

IR50 grown during 1985 wet season was

Space limitations prevent IRRN from publishing solely yield data and yield component data from routine germplasm screening trials. Publication is limited to manuscripts that provide either a) data and analysis beyond yield and yield components (e.g., multiple or unique resistances and tolerances, broad adaptability), or b) novel ways of interpreting yield and yield component data across seasons and sites.

Table 2. General agronomic characters of IR46 and IR10781-143-2-3 under transplanted rainfed lowland conditions in subtropical Nepal. a

Heading Maturity Culm length Panicles Av yield Variety (DAS) (DAS) (cm) (no./m 2 ) (t/ha)

IR46 108 135 96 229 3.4 IR10781-143-2-3 105 137 92 233 3.5 Masuli (most popular) 119 150 100 231 3.0 a DAS = days after seeding.

ha under rainfed lowland conditions (the crops such as wheat, winter maize, or national average rice yield is 2.2 t/ha). winter legumes. They are resistant to

earlier than Masuli in the normal (Jun- They are being distributed to farmers Oct) planting season (Table 2), giving through the rice minikit program. enough time for farmers to plant winter

Both entries mature at least 10 d major diseases bacterial blight and blast.

Harvesting 27 d after 50% anthesis gave AF-P bags, and had higher electrical con- the lowest electrical conductivity and ductivity. The interaction was significant. highest germination (see table). Harvesting The increased electrical conductivity of 41 d after 50% flowering gave the highest seeds harvested 41 d after 50% anthesis in electrical conductivity and lowest germina- storage showed that they are less vigorous tion. Seeds stored in cotton cloth bags and deteriorate faster than seeds harvested deteriorated more than those stored in P- 27 d after 50% anthesis.

Electrical conductivity of IR50 seeds stored for 9 months. National Pulses Research Centre, Vamban, India, 1985 wet season.

Electrical conductivity a (dS/m)

Harvest date At 3 mo after 6 mo after 9 mo after Germi- (d after harvest harvest harvest harvest Mean nation

50% anthesis) (%) C1 C2 C1 C2 C1 C2 C1 C2

27 Untreated Treated



Mean Germination(%) LSD (0.01)

36.85 36.83 36.83 36.83

39.41 39.41 39.41 39.41

48.64 48.64 48.64 48.64

41.63 41.63 94 94

0.63 0.59

a C1 = cotton bags, C2 = P-AF-P containers.

37.61 37.12 39.62 37.18 40.20 37.25 37.83 93 37.26 37.10 39.80 37.16 40.18 37.20 37.80 96

40.68 39.86 41.86 40.75 44.86 41.86 41.08 92 41.61 39.68 42.12 39.86 43.86 40.28 40.78 95

53.63 49.24 55.32 51.24 61.23 51.83 52.47 89 50.24 49.07 54.83 50.61 60.20 51.61 51.73 90

43.51 42.01 45.59 42.80 48.42 43.34 91 94 90 90 89 94

0.39 0.39 0.55 0.39 0.38 0.45 0.45 0.32

Mid-storage correction to prolong viability of rice seeds

C. Dharmalingam, Agricultural College and Research Institute, Madurai 625104, Tamil Nadu, India

We stored seeds of rice cultivars ADT36. Bhavani, and CO 40 at 8.5% moisture content in cloth bags under ambient

conditions. After 8 mo, half the seeds were soaked in double their volume of a dilute sodium dihydrogen phosphate solution (10 -4 M) for 6 h, sun-dried to 8.5%, and re-stored for 24 mo.

Hydrated seeds maintained high germination and vigor (in terms of root length) (see table). Nonhydrated seeds lost vigor and viability. Medium-duration cultivar Bhavani had lower storage potential than CO 40 and ADT36.

IRRN 15:3 (June 1990) 21

In a pot study, we evaluated the effect of incorporating residues of mesquite ( Prosopis glandulosa ), withania ( Withania somnifera ), and country mallow ( Abutilon indicum ) with rice ( Oryza sativa ) husks and wheat ( Triticum

Germination and vigor of hydrated rice seeds after 3 periods of storage. Tamil Nadu, India.

aestivum) and rice straw, neem

After storage

( Azadirachta indicum ) leaves, and farmyard manure on straw and grain yields of rice. Soil had pH 7.6, 0.95%

Cultivar Parameter Initial 8 mo Biological

duration 12 mo 32 mo loss (%)

Control Hy- Control Hy- Control Hy- Control Hy- drated drated drated drated

ADT31 Short Germination 86 82 90 73 89 45 85 47.7 1.2

Root length 19.5 17.6 22.1 15.0 20.0 9.2 17.8 52.8 8.7 (%)

(cm) Bhavani

Medium Germination 90 84 95 75 86 16 85 (%)

(cm)

82.2 5.6

Root length 18.2 16.0 17.6 15.0 19.5 10.4 18.2 42.8 –

CO40 Germination 89 86 94 78 88 27 87 69.7 2.2

Root length 20.7 18.9 21.1 17.7 20.2 11.5 19.0 44.4 8.2 (%)

(cm)

CROP AND RESOURCE MANAGEMENT Soil microbiology

Influence of wild plant and crop residues on rice yield

S. M. Alam and A. R. Azmi, Atomic Energy Agricultural Research Centre, Tandojam, Pakistan

Plant residues and farmyard manure are added to soils to improve their organic matter content and productivity. This traditional agricultural practice has primarily been used to increase soil humus content, water-holding capacity, water infiltration rate, aeration, and porosity; to ameliorate soil temperature; and to supply some essential plant nutrients.

organic C, 0.073% N, 9.7% CaCO 3 , 0.15% TSS. Each pot held 8 kg soil.

For the wild plants, treatments were 3 g residue/kg soil (about 6 t/ha) plus 25 mg N/kg (about 50 kg N/ha). For the crop residues, treatments were 3 g residue/kg soil plus 50 mg N/kg soil. Each pot also received 25 mg P/kg soil. Rice cultivar Shadab was transplanted at 4 seedlings/ pot. Pots were arranged in a randomized block design with four replications. N application was lower for the wild plants because their very high antibiotic activi- ties tended to inhibit nitrification.

Effect of incorporating plant residues on rice straw and grain yieids. a

Straw yield Grain yield Treatment b (g/pot) (g/pot)

Control (no residue) 17.45 c 11.70 b Mesquite 28.80 a 24.97 a Withania 23.92 b 19.62 a Country mallow 24.62 b 22.00 a Rice husk 16.05 c 11.62 b Wheat straw 16.92 c 10.75 b

Neem leaf 18.05 c 12.10 b

Farmyard manure 17.92 c 10.22 b 25.22 b 20.67 a

a In a column, means followed by the same letter are not significantly different (DMRT p<05). b Plant residue and farmyard manure were applied at 3 g/kg soil.

22 IRRN 15:3 (June 1990)

Straw and grain yield increased significantly with incorporation of mesquite, withania, and country mallow residues, and of neem leaf (see table).

Effect of seeding rate on dry matter production and nitrogen accumulation of Sesbania rostrata

K. H. Diekmann and S. K. De Datta, Agron- omy Department, IRRI

Increased crop seeding rates result in increased plant competition for nutrients and light. We evaluated the effect of different seeding rates on dry matter production and N accumulation in Sesbania rostrara, a stem-nodulating legume and potential green manure crop for lowland rice.

The field experiment was conducted in 1987 wet season. Soil was a Maahas clay (Tropaquept) with pH 6.3; 11 g organic C/kg; 1.2 g total N/kg; and cation exchange capacity, 34 cmol/kg. P (20 kg/ ha) as single superphosphate was broadcast and incorporated before seeding. Seeding rates were 20, 30, 40, and 50 kg sesbania seeds/ha, laid out in a factorial randomized complete block design with four replications. Plot size was 20 m 2 .

with concentrated sulfuric acid were broadcast into well-leveled, water- saturated soil. The field was kept saturated to 7 d after seeding, then flooded to 0.05 m.

Sesbania was harvested 45 d after seeding. Plant fresh and dry weights were measured and plant density determined from a 7-m 2 area A subsample (4 × 1 m per plot) was taken to determine leaf and stem dry matter separately and to analyze N concentrations in leaf and stem. Total N accumulation was calculated.

N concentrations in leaf and stem did not differ significantly with seeding rate (see table). Seeding at 40 kg/ha gave the highest total N accumulation per plant (114 kg N/ha), and highest fresh and dry matter production. Seeding at 50 kg/ha gave lower fresh and dry matter production and N accumulation than seeding at 40 kg/ha.

Sesbania seeds pretreated for 30 min

Rice straw

Long

Triacontanol increases plant height and weight within a few days of application and stimulates nutrient assimilation.

IR42 and tall indica NC492 rice varieties were soaked 1 h before sowing in 3 concentrations of TRIA (n-Triacontanol): 0.01, 0.10, and 1.00 ppm, with three replications. Root length, root volume,

Seeds of semidwarf IET4094 and

Plant density, dry matter production, N concentration, and N accumulation of Sesbania rostrata at different seeding rate IRRI farm, Philippines, 1987 wet season.

Dry matter Plant Total Seeding rate (mg/ha) density Leaf N Stem N plant N

(kg/ha) (plants/m 2 ) (g/kg) (g/kg) (kg/ha)

20 1.2 2.7 55 46 9 81 30 1.3 3.0 70 46 8 85 40 1.6 4.1 107 47 9 114 50 1.5 3.9 119 46 8 100

LSD (0.05) 0.1 0.3 10 2 1 8

Leaf Stem

These results suggest that the higher plant densities resulting from seeding rates above 40 kg/ha decrease organic matter production and N accumulation of sesbania plants. A plant density of 100 plants/m 2 seems to be optimum for maximum N accumulation.

To achieve a plant density of about 100 plants/m 2 , seeding rates may have to be adjusted for soil textures, climates, and field conditions.

~~

Physiology and plant nutrition

Effects of a growth regulator on rice seedling growth

J. Ahmed, Rice Research Station, Chinsurah, West Bengal, India

Growth regulator Triacontanol has been found effective in increasing biomass production in cereals and vegetable crops.

Effect of n-Triacontanol on rice seedling characters.

seedling height, seedling dry weight, and leaf number were recorded 25 d after seeding.

In general, seedlings treated with TRIA were superior to those with no treatment (see table). Late-maturing NC492 and IR42 showed better results than medium-maturing IET4094 in all treatments, for all characters. No toxic, abnormal, or atypical morphological changes were observed at the concentrations used.

Root length (cm/plant) Root volume (ml/plant) Seedling height (cm/plant) Leaf no. per seedling Seedling dry wt (mg/plant)

(mg/liter) lET4094 IR42 NC492 IET4094 IR42 NC492 IET4094 IR42 NC492 IET4094 IR42 NC492 IET4094 IR42 NC492

0.00 21.2 15.3 17.6 0.2 0.1 0.2 27.4 20.2 37.4 4.9 4.1 4.2 114 137 211 0.01 21.8 21.5 19.5 0.3 0.3 0.3 27.7 25.2 38.6 4.9 4.9 4.7 171 219 237 0.10 21.8 18.6 20.4 0.3 0.2 0.5 27.6 24.1 39.5 5.0 4.9 4.4 181 207 253 1.00 21.8 18.6 18.1 0.3 0.3 0.3 27.6 23.9 37.8 5.0 4.9 4.5 186 202 217

CV (%) 7.8 10.1 4.2 2.9 5.8

n-Triacontanol

LSD (0.05) 2.6 0.1 2.1 0.2 18

Fertilizer management Greenhouse evaluation of urea supergranules (USG) containing diammonium phosphate (DAP) for transplanted rice

N. K. Savant and S. H. Chien, International Fertilizer Development Center (IFDC), P.O. Box 2040, Muscle Shoals, Alabama 35662, USA

Serious losses of fertilizer N and P to runoff are common in transplanted rainfed ricefields of small farmers in South and Southeast Asia. Losses occur primarily because farmers are unable to properly incorporate fertilizers into soils with varying depths of nonflowing or

flowing floodwaters. A ready-made, balanced NP fertilizer and an alternative application method are needed.

Ca(H 2 PO 4 ) 2 . H 2 O (such as single or triple

superphosphate [TSP]) are not compatible with urea because of an adduct formation that leads to poor physical quality and caking of USG briquettes. DAP, a common fertilizer for transplanted rice in tropical rice-growing countries, is compatible for preparation of USG. Agronomi- cally, deep placement of USG is efficient in transplanted rice.

We conducted a greenhouse experiment to evaluate basal deep-placed USG containing DAP as NP fertilizer in transplanted rice. The experiment was laid out in a randomized block design with four replications. Soil was Vernon clay (Typic

Phosphatic fertilizers containing

Ustochrept, pH 8.0, CEC 33.0 cmol c /kg), which in earlier experiments had respon- ded to applied N and P. For a blanket basal application, 100 mg K/kg (as KC1) and 25 mg Zn/kg (as ZnSO 4 ) were incorporated into the soil before transplanting.

hill) of IR36 were transplanted (20- × 20- cm spacing) in 2-wk presubmerged and puddled soil (32 kg air-dried basis) in a wooden box (40- × 40- × 30-cm inside dimensions) with plastic lining. USG containing DAP (as tablets) was prepared by compacting a mixture of prilled urea (PU) and DAP in a 1:2 proportion. The amounts of N and P used (19.3 mg N/kg and 10.3 mg P/kg, equivalent to 40 kg N and 21 kg P/ha on area basis) were on the steep portion of their response curves for the soil used.

Four hills (three 3-wk-old seedlings/

IRRN 15:3 (June 1990) 23

Effect of deep-placed USG containing DAP on grain yield and N and P uptake by transplanted IR36. Greenhouse experiment, IFDC, USA, 1988.

Uptake by grains b

(g/4 hills per box) Grain yield b

Treatment a (g/4 hills per box) N P

Check 97 c 1.30 e 0.16 d USG deep placed at transplanting 130 b 1.78 cd 0.18 d TSP incorporated before transplanting 128 b 1.61 d 0.31 ab PU+DAP incorporated before transplanting 150 a 1.93 abc 0.32 a DAP incorporated before transplanting + PU 152 a 2.04 ab 0.31 ab

topdressed at panicle initiation

remaining N as USG deep placed at transplanting DAP incorparated before transplanting + 150 a 1.89 bc 0.34 a

TSP incorporated before transplanting + USG 157 a 2.13 a 0.26 bc

USG containing DAP deep placed at transplanting 152 a 2.06 ab 0.26 c PAPR incorporated before transplanting + USG 147 a 2.07 ab 0.24 c

deep placed at transplanting

deep placed at transplanting a Rates of application: 19.3 mg N and 10.3 mg P/kg soil; 619 mg N and 329 mg P/4 hills per box. Estimated rate (on area basis),

means broadcast and incorporation up to 5-cm depth before transplanting with practically no floodwater. Fertilizer analysis: PU and USG, 46% N; DAP, 21.2% N and 23.5% P; TSP, 20.9% total P; and PAPR from Central Florida (25% acidulation with H 3 PO 4 ), 15.0% total P. b Means in a column followed by the same letter are not significantly different at the 5% level by DMRT.

40 kg N and 21 kg P/ha. One USG was placed at 110-cm depth in the center of 4 rice hills with 20-*20-cm spacing. Incorporation

Plant growth the first 3-4 wk after transplanting was markedly slower for deep-placed USG containing DAP (see table). However, grain yields and N and uptake were statistically on a par with those for incorporated DAP, TSP, or partially acidulated phosphate rock (PAPR) and deep-placed USG. The PAPR used was as effective as TSP in P availability.

These data suggest that deep-placed USG containing appropriate amounts of DAP may be a judicious choice as a NP fertilizer for small farmers in transplanted rice areas, especially rainfed, where adequate incorporation of fertilizers is not possible because of uncontrolled floodwater and nonavailability of suitable imple- ments. Research under field conditions is under way in India to verify this.

Rate and time of N application for direct seeded irrigated rice

O. S. Kandasamy and SP. Palaniappan, Tamil Nadu Agricultural University, Coimbatore 641003,India

We evaluated rate and time of N application for irrigated rice on a clay loam soil. Soil had pH 7.3 and 0.42% organic C. Treatments were N at 0, 40, 80, and 120 kg/ha in kuruvai (Jun-Sep) and 0, 50, 100, and 150 kg/ha in thaladi (Oct-Feb) and samba (Sep-Jan) seasons, and the initial half of the N applied at four different times in kuruvai (at 10, 20, 30 d after seeding [DAS] and at active tillering) and at five different times in thaladi and samba (at sowing; 10, 20, 30 DAS; and at active tillering). The remaining 50% of N was applied in two equal doses at active tillering and panicle initiation stages, except in treatments where the initial dose itself was applied at active tillering. In this treatment, N was applied in two splits, half at active tillering and half at panicle initiation.

N was broadcast as urea. Basal fertilizer was incorporated in dry soil during kuruvai and samba when dry seeding was done, and in the puddle

Yield and panicles/m 2 of direct seeded rice with graded rates and time of N application, Aduthurai, India.

Treatment Kuruvai Thaladi Samba

Panicles Grain Panicles Grain Panicles Grain (no./m 2 ) yield (no./m 2 ) yield (no./m 2 ) yield

(t/ha) (t/ha) (t/ha)

N rate (kg/ha) Kuruvai Thaladi and

Samba 0 0 289 2.5 236 1.6 307

40 50 327 4.3 308 2.8 374 4.5 3.2

80 100 362 5.0 332 3.3 434 120 150 383 5.2 351 3.5 453 5.3

5.1

LSD (0.05) 10 0.2 25 0.15 17 0.15

Time of application (initial 50% N)

At sowing 328 3.1 421 10 DAS

4.9 356 4.8 343 3.5 434 5.0

20 DAS 384 5.4 339 3.3 470 5.5 30 DAS 346 4.7 325 3.1 398 4.7 At tillering 343 4.4 317 3.0 378 4.6

(LSD 0.05) 12 0.2 ns 0.19 22 0.19

during thaladi when wet seeding was In general, yields increased with N done. Water was maintained at 2-3 cm application in all three seasons (see table). for topdressing. The responses to N application fitted

factorial randomized block design with Kuruvai Y = 2.6 + 0.05 N - 0.0003 N 2

three replications. Short-duration TKM9, Thaladi Y= 1.6 + 0.03N - 0.0001 N 2

medium-duration IR20, and long- Samba Y = 3.1 + 0.03N - 0.0001 N 2

duration CR1009 were sown in kuruvai, The initial 50% N could be applied 20 thaladi, and samba, respectively. Dry DAS in kuruvai and samba when dry seeds were broadcast during kuruvai and seeding was done, and 10 DAS in thaladi samba; sprouted seeds were broadcast on when sprouted seeds were sown in puddled soil in thaladi. puddled soil.

The experiments were laid out in a quadratic functions.

24 IRRN 15:3 (June 1990)

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Influence of modified urea and placement on N use in irrigated rice

R. Singh, S. K. Shrivastava, and J. M. Pandagare, IGKVV, College of Agriculture, Raipur 492012, Madhya Pradesh, India

Numerous N response experiments have shown that fertilizer N recovery by rice is seldom higher than 30-40%; even with the best agronomic practices and strictly controlled conditions, recovery seldom exceeds 60-65%. Using urea supergranules (USG) or urea briquettes, deep placed, has increased N efficiency, and crop response to sulfur-coated urea (SCU) has generally been superior to response to urea in a single dose and often to split applications.

USG, and best split urea at different N levels in a randomized block design with four replications. The 4-yr experiment (1981-84) used medium-duration Asha and Usha as test varieties. Soil was a Vertisol, clay loam texture, with pH 7.0,1.3% organic matter, 11% total N, and CEC 33 meq/100 g. Exchange-

We compared the efficiency of SCU,

Influence of modified urea materials at different N rates on estimated wetland rice soil ammonium-N and nitrate-N

P. C. Pandey, G. L. Sharma. Pyare Lal, and P. S. Bisht, Agronomy Department, G. B. Pant University of Agriculture and Technology, Pantnagar Nainital 263145, Uttar Pradesh, India

Changes in NH 4 + -N and NO 3

- -N levels in wetland soil can provide valuable insights into N losses and availability of N for rice. The NH 4

+ -N And NO 3 - -N at 0-15 cm

depth in flooded soil were measured at 15, 30, 45, and 60 d after transplanting (DT).

The experimental area was Aquic Hapludoll (Mollisol of Tarai moist plains region about 30 km south of the foothills of the Shivalik Range of the Himalayas). Soil was silt loam with pH 7.9, 1.2% organic C, 0.1% total N, 8 ppm available

Grain yield with different modified urea materials, placement techniques, and nitrogen levels. Ralpur, India (1981-84 wet seasons).

Grain yield(t/ha) N(kg/ha) Urea form a

1981 1982 1983 1984 Mean

0 29 58 87

116 Mean

29 58 87

116 Mean

29 58 87

116 Mean LSD (0.05) CV (%)

PU PU PU PU PU

SCU SCU SCU SCU SCU USG USG USG USG USG

2.0 2.3 2.4 2.8 2.9 2.6 2.6 3.1 3.2 3.7 3.2 2.4 2.7 2.8 3.1 2.7 0.4 9.5

2.6 3.1 3.6 3.4 3.9 3.5 3 3 4.0 4.0 4.4 3.9 3.6 3.6 4.1 3.6 3.7 0.7

11.2

1.9 2.7 3.0 3.4 3.7 3.2 3.2 3.8 4.2 4.5 3.9 3.2 3.7 4.1 4.3 3.8 0.4 7.2

2.0

3.9 4.4 4.4 4.2

4.0 4.2 4.5 4.3

4.3 4.6 4.8 4.6 2.6

10.5

2.1 2.7 3.2 3.5 3.7 3.4 3.0 3.7 3.9 4.3 3.8 3.1 3.6 3.9

3.7 4.0

a PU was applied as best split, SCU was broadcast and incorporated, USG was placead 10-12cm deep in the soil

able bases (in meq/100 g) were 0.07 Na, 10-12 cm deep, and prilled urea (PU) best 0.63 K, 4.7 Mg, and 27 Ca. Available P split (see table). Yields increased with was 17 ppm by Bray method and 4 ppm increased N. by Olsen. Available Zn was 2.7 ppm. Highest N use efficiency was 32.1 kg

Maximum yields at all N levels were grain/kg N as USG at 29 kg N/ha. Aver- obtained with SCU broadcast and aged over N levels, maximum N use effi- incorporated, followed by USG placed ciency was 18.7 kg grain/kg N as SCU.

1. NH 4 + -N content in soil as influenced by N rates (a) and sources (b).

lRRN 15:3 (June 1990) 25

- -

-

-

NH 4 + -N, and 10 ppm available NO 3 - -N. Pant Dhan 4 (134 d duration) was transplanted during 1985 and 1986 wet seasons (May-Oct).

Urea supergranule (USG), sulfur- coated urea (SCU), and Musoorie phos- coated urea (MPCU) as basal incorporated and prilled urea (PU) applied as local split (1/2 at transplanting, 1/4 at tillering, 1/4 at 5-6 d before panicle initiation [DBPI]) and standard split (2/3 at transplanting and 1/3 at 5-6 DBPI) were applied at 29, 58, and 87 kg N/ha. MPCU and SCU were broadcast and incorporated at transplanting, USG was hand placed 8-10 cm deep in the center of 4 hills.

Soil samples were collected randomly from fertilized plots, except in USG plots where they were collected 6-8 cm away from the placement site.

NH 4 + -N and NO 3 - -N were extracted from the wet soil immediately with 1N sodium sulfate. NH 4 + -N concentration was determined by modified Nessler reagent method and that of NO 3 - -N by chro- motropic acid method.

NH 4 + -N content increased with increasing N rates to 30 DT, then decreased (Fig. 1). The decrease may be attributed to uptake by plants, gaseous loss of NH 3 , and nitrification-denitrification. The decrease was less with USG.

15 DT, it was higher with PU and MPCU than with USG and SCU (Fig. 2). Plots with USG showed lower NO 3 - -N, pre- sumably because the USG was placed in a reduced zone where nitrification might be limited for lack of oxygen. With SCU, low concentration of NO 3 - -N could be due to delayed release of urea and conversion of fertilizer N to NO 3

- .

NO 3 - -N concentration was very low. At

Contribution of flood siltation to boro rice yield and response to N and K

M. Amin and M. Sadrul Amin, On-Farm Research Division, Bangladesh Agricultural Research Institute, Thakurgaon, Bangladesh

Floodwater deposits silt and other sus- pended materials as it starts to recede. The effects of this silting on soil productivity have not been established experi- mentally.

26 IRRN 15:3 (June 1990)

2. NO 3 - -N content in soil as influenced by N rates (a) and sources (b).

The presence of nitrate suggests that These results suggest that formation of nitrification-denitrification losses may be soil nitrate can be reduced slightly through occurring. the use of modified urea materials.

We evaluated the effects of siltation ponded by floodwater about 1.5 m deep by floodwater on boro rice in terms of the for about 15 d. crop’s response to N and K fertilizer Jan- After the flood receded, three types of Apr 1988. Land within the Hathazari soil sampling were done: deposited Farming Systems Research area was surface silts, 2.5 cm; original soil, 2.5-15

Table 1. Characteristics of soil sample of flash-flooded ricefields Hathazarl, Bangladesh Jan 1988.

Organic K NH 4 -N Zn S Soil sample pH matter (%) (meq/100 ml) (lg/ml) (lg/ml) (lg/ml)

0-2.5 cm surface silt 6.6 2.35 1.0 22.5 3.0 8 2.5-15 cm soil 5.9 2.45 0.3 17.5 2.5 4 0-15 cm silt and soil 6.0 2.50 0.3 19.5 3.0 7

~~~~ ~

cm; and whole sample, 0-15 cm. Soil analytical data are presented in Table 1.

Eight fertilizer levels were tested (Table 2) in a randomized complete block design with four replications.

All the P and K, and 1/3 the N were applied basally after final land preparation. The remaining N was topdressed, 1/3 at 25 d after transplanting (DT) and 1/3 at 45 DT. Purbachi rice seedlings (35 d old) were transplanted at 25- × 15-cm spacing. Application of 120 kg N, 34 kg K/ha gave the highest yield. No significant yield differences were found when K was applied at 17-51 kg/ha with 80-120 kg N/ ha (Table 2). The relatively low effect of K on grain yield may be attributed to the increased K content of the surface silts.

Response of rice to Azospirillum brasilense and organic manures on organic- and chemical-fertilized farms in India

R. Subramanian and M. Rangarajan, Agricul- tural Microbiology Department, Tamil Nadu Agricultural University, Coimbatore 641003, Tamil Nadu, India

Field trials were conducted in lowland rice culture during Sep 1988-Feb 1989 on two farms in Pondicherry, India, using White Ponni rice variety. One farm (Gloria Land) had adopted organic farming 10 yr before. The other farm (farmer’s field) had for several years used only chemical fertilizers.

The field trials were laid out in a randomized block design with nine treatments and four replications. The control plots on the two farms differed; the farmer’s field plot received 100:50:50 kg NPK/ha. Other treatments included farmyard manure (12.5 t/ha), leaves of Azadirachta indica (6.25 t/ha), and cow dung slurry (5.0 t/ha) alone and in combination with A. brasilense (seed, seedling, and soil application).

with some treatments (see table). The Grain yield in Gloria Land increased

Table 2. Yield parameters of boro rice planted on flash-flooded fields and fertilized with N and K, Hathazari, Bangladesh, Jan-Apr 1988.

Treatment a Panicles Filled 1,000-grain (kg NPK/ha) (no./m 2 ) spikelets

Grain

(no./panicle) weight

(g) Yield (t/ha)

0-0-0 0-28-34

40-28-34 80-28-0 80-28-17 80-28-34 80-28-51

120-28-34

186.30 213.97 244.89 266.62 276.07 277.42 274.72 308.47

45.21 51.09 63.12 72.12 77.67 77.84 77.14 76.67

21.15 22.55 23.03 23.09 23.32 23.44 23.60 24.76

1.4 2.1 3.0 3.7 4.1 4.1 4.2 4.4

CV (%) 12.44 11.44 2.05 7.3 LSD (0.01) 63.74 15.49 0.50 0.5

a From urea, triple superphosphate, and muriate of potash.

Response of White Ponni rice grown in organically and chemically fertilized fields. a Pondicherry, India Sep 1988-Feb 1989.

Grain yield (t/ha) Straw yield (t/ha) Treatment

Gloria Land

Farmer’s field

Gloria Land

Farmer’s field

No addition

Farmyard manure (FYM)

Green leaf manure (GLM)

Cow dung slurry (CS)

Azospirillum

FYM + Azospirillum

GLM + Azospirillum

CS + Azospirillum

FYM + GLM + CS + Azospirillum

100 N-50 P-50 N

LSD

5.7

5.9 (3.15) 6.7

(17.7) 6.1

(6.1) 5.9

(2.6) 6.2

6.8 (1 8.2)

6.2 (8.6) 6.8

(1 9.2) 0.4

(9.1 )

5.1 4.4

4.1

4.0

4.1

5.1 (1.2) 4.9

4.9

5.7 (13.3)

0.2

8.1

8.8 (7.5) 9.9

(2 1.9) 8.7

(7.1) 7.5

8.8 (8.2) 9.8

(19.8) 9.8

(20.5) 10.4

1.7 (28.3)

7.4 6.9

6.5

6.4

6.5

7.0

6.9

6.4

7.6 (3.7) 0.5

a Figures in parentheses indicate percentage increase.

effect on yield of different organic higher grain yield than N fertilizer alone. manures with or without Azospirillum In Gloria Land, where organic manures brasilense varied, depending upon the N had been applied for several years, Azos- content of the organic manures. In the pirillum application did not have a signifi- farmer’s field, N fertilizer yielded less cant effect. In the farmer’s field, Azos- than the control plot of Gloria Land. pirillum application increased grain yield Combined application of organic manures significantly. Straw yields followed a plus A. brasilense gave significantly similar trend.

Surveys of disease or insect incidence/severity in one environment are useful only if the information is related to other variables (e.g., climatic factors, crop intensification, cultivars, management practices, etc.). By itself, information on incidence in one environment does not increase scientific knowledge.

IRRN 15:3 (June 1990) 27

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Crop management

Effect of traditional and improved nursery methods on seedling growth and rice yield

M. V. Zagade, S. A. Khanvilkar, and B. P. Patil, Agronomy Department, Konkan Krishi Vidyapeeth, Dapoli 415712, Dist. Ratnagiri (MS), India

In the Konkan region of Maharashtra, rice seedlings traditionally are raised on a flat nursery bed on which a large quantity of cow dung, twigs of trees ( Terminalia spp.), dry grass, and dry leaves of forest trees have been burned. To further increase soil temperature, burning is slowed by spreading a thin layer of fine soil on top of the organic matter.

bushes are cut to collect organic matter. That eventually depletes the forests and degrades the soils. In the summer, skeletons of Terminalia trees and burned patches of fields are common sights.

Weed control seems to be the only objective of this traditional method. Although the seedlings raised are vigorous, long-term detrimental effects do not warrant the short-term advantages.

Each year, branches of forest trees and

We evaluated the traditional method against improved methods of raising seedlings in two consecutive experiments during 1988 wet season. Treatments included preburning of nursery bed and raised and flat nursery beds with various mechanical and herbicidal weed control treatments (see table).

The experiment was laid out in a randomized block design with three replications. Soil of the experimental plot was lateritic having 152.5, 6.9, and 248.9 kg available N, P, K/ha. Plot sizes were 6 × 1 m for the nursery and 4.6 × 4.2 m for transplanting. Nursery area burning was done in May 1988 and Ratnagiri 24 was planted in Jun 1988. Preemergence herbicides were applied on wet soil.

Seedlings from the set of nursery treatments were transplanted in a different field in a randomized block design with three replications. Recom- mended plant population (20 × 15 cm), fertilizers (100 kg N, 22 kg P/ha), and plant protection measures were applied uniformly to all treatments.

Seedling height and dry matter in the traditional rice nursery were more than twice that in the other nursery treatments (see table). This could be attributed to increased availability of N (l0%), P (39%), and K (100%). Also, all weeds were eliminated.

However, the pretransplanting differences did not significantly affect crop yields. Seedlings from the traditional nursery were not superior to seedlings from improved nurseries.

Thus, the traditional method benefits only the nursery and should be discour- aged to save valuable organic matter and vegetation. Instead, herbicides should be used to control weeds in the nursery.

Integrated pest management–diseases

Nonfluorescent Pseudomonas strains causing rice sterility and grain discoloration in Colombia

R. S. Ziegler and E. Alvarez, Rice Program, Centro Internacional de Agricultura Tropical (CIAT), Apartado Aereo 6713, Cali, Colombia

Two nonfluorescent species of Pseudo- monas, P. avenae and P. glumae, cause seedling rot, grain discoloration (GlD), and sterility in rice. P. avenae is known to be distributed worldwide; until a recent report from Latin America, P. glumae was known only in Asia. Reports on the

Effect of preburning nursery bed and raised and flat bed nurseries with different weed control methods on seedling growth and transplanted rice yield. a

Treatment Seedling Dry matter/ D ry weight Weed control Available Available Exchangeable Grain Straw height seedling of weeds efficiency N P K yield yield (cm) (mg) (t/ha) (%) (kg/ha) (kg/ha) (kg/ha) (t/ha) (t/ha)

Rabbing (preburning) Raised bed + unweeded control Raised bed + weed-free check Flat bed + unweeded control Flat bed + weed-free check Raised bed +one hand weeding Flat bed + one hand weeding Raised bed + 3.0 kg ai butachlor

50 EC/ha at preemergence Flat bed + 3.0 kg ai butachlor

50 EC/ha at preemergence Raised bed + 3.0 kg ai butachlor

10% G/ha at preemergence Flat bed + 3.0 kg ai butachlor

10% G/ha at preemergence Raised bed + l.0 kg ai oxadiazon/ha

at preemergence

at preemergence LSD (0.05)

Flat bed + l.0 kg ai oxadiazon/ha

10.5 5.8 6.3 5.7 6.0 5.8 5.7 5.3

5.5

4.9

5.7

4.9

5.9

1.1

115.0 42.0 47.3 40.0 46.3 49.3 46.3 34.6

36.0

33.6

38.0

37.0

41.0

9.9

1.2 0.3 1.4 0.3 0.3 0.3 0.2

0.2

0.2

0.2

0.2

0.2

0.1

100 13.3 75.9 0.0

75.9 76.3 75.9 85.1

84.7

85.1

84.7

85.5

85.1

168.7 152.7 153.5 156.1 150.3 153.1 152.6 146.1

146.1

144.9

151.4

151.4

154.3

6.5

9.9 6.8 7.1 6.9 7.2 7.0 6.9 7.0

7.1

6.9

6.9

7.0

6.9

0.6

439.1 233.8 224.0 237.2 237.2 240.5 233.1 238.7

241.8

234.4

238.8

229.2

237.3

25.4

2.4 3.0 2.4 2.8 2.8 3.2 2.3 2.8 2.8 3.1 2.8 3.0 2.3 2.8 2.2 2.6

2.1 2.8

2.3 2.7

2.2 2.7

24 2.8

2.5 2.9

ns ns

a Nursery variables measured at time of uprooting seedlings.

28 IRRN 15:3 (June 1990)

-

characteristics of these species differ. We undertook to more completely character- strains reported as P. glumae found in Latin America. We also compared the characteristics of the two species to clarify some discrepancies in published descriptions.

Three strains of a nonfluorescent pathogenic bacterium obtained from discolored rice grains collected from farmers’ fields in Colombia were compared with four culture collection strains of P. glumae and 25 strains of P. avenae (6 culture collection strains and 19 strains previously identified at CIAT), using standard bacteriological techniques. The culture collection strains included type specimens of each species.

The pathogenic strains recovered from discolored grains were consistent with P. glumae, rather than with P. avenae (see table). All strains tested could be distin- guished from Erwinia herbicola in that they did not grow anaerobically and had multiple polar flagella. However, some differences were observed among the field-collected strains and the strains of known identity, as well as differences from published characteristics of the species.

The original description of P. glumae referred to it as producing a fluorescent pigment on potato agar. This probably referred to the diffusible green nonfluorescent pigment that we and others have observed to be produced by some, but not

Phenotypic characteristics a three Pseudomonas strains that cause grain discoloration and sterility in Colombian ricefields compared to strains of P. glumae and P. avenae.

P. glumae Colombian strain Phenotypic character (4 strains) (25 strains)

P. avenae

1445-4-1 1445-4-2 1462-7-2

Fluorescent pigment Arginine dihydrolase Nitrate reduction Oxidase Diffusible green pigment Accumulation of poly-b-

Utilization for growth

hydroxybutyrate crystals

Arabinose Cellobiose Raffinose Sucrose

Adonitol Inositol Sorbitol Arginine Salicine

Acid from Dextrose Lactose Sucrose Mannitol

H 2 S from TSI Catalase Gelatin liquefaction Growth at 41°C Growth in 5% NaCl Indole Lecithinase Levan from sucrose Lipase Pit formation on CVP Starch hydrolysis Tobacco hypersensitivty Pathogenicity on rice

Xylose

d (50) +

+ + +

d (75) + +

d (75) d (75)

+

d (75)

+

d (75) d (50)

+ +

+

+ +

+

+ +

+ + +

+ + +

+ +

+

+

+ + + +

+

+ +

+

+ +

+ + +

+ + +

+ +

+

+

+ + + +

+

+ +

+

+

+ + +

+ + +

+ +

+

+

+ + + +

+

+ +

+ +

+

d (60)

+

+

+

d (76)

d (76) +

+ +

+ + +

a + = 90% or more of strains positive, - = 90% or more of strains negative, d = 11-89% strains positive; number in parentheses is percent of strains positive.

all strains. The growth limit for P. glumae has been reported to be 40 °C; however, the strains in this study all grew at 41°C.

the synonymy of P. alboprecipitans and P. setaria with P. avenae ( P. menae is now considered to be the correct name far this pathogen), described their strains as oxidase negative. More recently, researchers in Japan described their strains as oxidase positive. We have found our strains to be oxidase positive.

The Japanese researchers also reported that their strains grew in 3% NaCl but not in 5% NaCl. Our strains grew in 5% NaCl. The Japanese reported negative tobacco hypersensitivity, lipase, and H2S production. Our strains were positive, negative, and variable, respectively. The strains we identified as P. avenae and P. glumae also abundantly accumulated

Researchers in the U.S., in establishing

poly-b-hydroxybutyrate crystals.

False smut incidence on rice relative to plant characters and environmental factors

C. L. Bhardwaj, Regional Research Station, Himachal Pradesh Krishi Vishvavidyalaya, Bajaura (Kullu)-175125, India

We studied false smut Ustilaginoidea virens Tak. incidence on 32 rice cultivars and the relationship of disease severity to plant characters and ambient environmental factors in the 1987 dry season. Rice cultivars were dry seeded in upland conditions, in a completely randomized block design with three replications. False smut of panicles at maturity was recorded for each cultivar. Disease severity, infected panicles, and number of infected florets on the most infected panicle were recorded.

HPU2202, HPU5101, Nag 1-38, VL 501, and VRS1 were disease free. Disease severity on the 26 susceptible cultivars ranged from 1 to 17.9%. A significant negative correlation ( r = -0.54) between plant height (range 70-135 cm) and disease severity indicated that short cultivars were more vulnerable than tall ones.

days to 50% flowering was not signifi-

B3719C-TB-8-1-4, China 988,

The correlation of disease severity and

IRRN 15:3 (June 1990) 29

- - - - -

- - - - -

- -

- -

- - - - -

- -

- - - - -

- - - - - - - - - -

- - - -

-

- - - - - -

- - - - - - - - - - - - - - - - - - -

Laboratory examination revealed the presence of Fusarium moniliforme Sheld., the imperfect stage of Gibberella fijikuroi (identified on the basis of micro and macro conidia, micro conidiophores, and micro conidial chains). A pathogen-

icity test to fulfill the requirements of Koch’s postulates confirmed F. moniliforme to be the causal organism.

This is the first report of this disease in Pakistan.

In ricefields, wolf spiders Lycosa pseudoannulata respond to high densities of prey, particularly brown planthopper (BPH) Nilaparvata lugens (Stål). This increases the chances that spiders will encounter each other while hunting for prey. That may decrease searching efficiency per predator and increase a tendency toward aggression, cannibalism, and outward dispersal. Such encounters between searching predators are often called “mutual interference.”

We conducted laboratory experiments to measure mutual interference among wolf spiders and to determine the effect of hopper density on encounters between

spiders. Freshly emerged BPH adult females were placed inside mylar cages (19-cm diam, 55-cm ht) with 5 tillers of TN1 potted rice plants at densities of 5, 10, 20, 30, and 60 BPH/cage. They were exposed to 1, 2, or 3 freshly emerged adult female wolf spiders for 24 h. There were 5 replications.

Searching efficiency per spider, a, over the experimental period was computed as

a = 1 /P 1n [ N /( N-N a )] where a is searching efficiency, P is predator number, N is initial number of BPH, and N a is number of BPH attacked Log of a was plotted against log of P to obtain a linear regression. The resulting relationship of this linear mode1 is

log a = log Q - m log P where Q and m are constants, characteristic of the predator.

K. L. Heong and E. G. Rubia, Entomology Department, IRRI

Linear correlations of false smut ( Ustilaginoidea virens ) disease incidence (percent panicles with false smut) on 32 rice cultivars and plant and environmental factors.

Correlation coefficient

( r ) a

Plant Plant height (cm) -0.54* Days to 50% flowering 0.095**

Environment a

Maximum temp d (28.1°C) -0.048 Minimum temp (20.1°C) -0.040 Relative humidity (87.8%) -0.321 Rainfall (1.4 mm) -0.120 Cloudiness (1.74 h) -0.176

Disease severity Number of false-smutted florets 0.81*

on the panicle with maximum infection

a P (0.05) = 0349*. b Av of 32 d during flowering.

cant. Correlations with environmental factors during flowering (22 Aug-29 Sep) were negative and nonsignificant (see table).

tion ( r = 0.81) of number of smutted florets on the panicle with the most infected florets and percent false smutted panicles was significant. The relationship between number of smutted florets on the panicle with the most infected florets and percent panicles with false smut (regression coefficient y = 1.26 + 0.763 x ) shows that, in assessing disease severity, one disease severity factor can be used to estimate another factor.

Among cultivars, the positive correla-

Bakanae and foot rot of rice in Punjab, Pakistan

L. K. Khokhar, National Agricultural Research Centre, Crop Diseases Research Institute, Islamabad, Pakistan

During a 1989 survey of rice crop diseases in Sialkot, Gujranwala, and Sheikhupura of Punjab Province, Basmati 385 growing in isolated farmers’ fields showed symptoms similar to those of bakanae disease. Some of the plants had yellowish green, thin leaves and exhibited abnormal stem elongation, lower tillering, and rotting at the root-stem joint as well as at the first node.

30 IRRN 15:3 (June 1990)

Efficacy of ethofenprox in preventing rice tungro (RTV) infection

N. V. Krishnaiah and A. Ghosh, Directorate of Rice Research, Rajendranagar, Hyderabad 500030, India

RTV transmitted by green leafhopper (GLH) Nephotettix virescens is one of the important diseases of rice in many parts of India. We studied the efficacy of ethofenprox (a new ether-derived insecti-

cide similar to synthetic pyrethroids) against GLH and RTV transmission.

Potted TN1 plants in controlled greenhouse conditions were sprayed with ethofenprox. At 0.01%, ethofenprox killed 78% of confined viruliferous adults within 30 min; plants sprayed with 0.01% recorded significantly lower RTV infection than plants sprayed with 0.05% monocrotophos (see table). GLH mortality within 30 min and RTV transmission were related; GLH mortality after 30 min was not related to RTV transmission.

Effect of ethofenprox and monocrotophos on green leafhoppers and RTV transmission. a

Insecticide GLH mortality (%) RTV

0.5 h 1.0 h 4.0 h 24 h (%) infection

Ethofenprox 0.01% 78 a 87 a 95 a 100 a 53 a Monocrotophos 0.05% 22 b 58 a 93 a 100 a 80 b Untreated control 0 c 0 b 0 b 2 b 100 c

a In a column, means followed by the same letter are not significantly different at the 5% level by DMRT.

Integrated pest management–insects

Mutual interference among wolf spider adult females

Regression analysis of the linear model log a = log Q - m log P in different prey densities.

Parameter estimate a

PH density m + s.e. log Q F P

5 0.439 ± 0.283 0.322 2.40 0.14* 10 0.556 ± 0.243 0.268 5.23 0.03* 20 0.103 ± 0.206 0.25 1 0.25 0.63 ns

30 0.486 ± 0.191 0.242 6.46 0.02* 60 0.707 ± 0.122 0.288 33.63 <0.01**

a ns = not significant, * = significant at p = 0.05, ** = significant at p = 0.01.

For BPH densities of 5 and 20, the aggregate at higher hopper densities regression was not significant It was increasing the chances of encountering significant for BPH densities of 10, 30, each other. At low hopper densities, the and 60 (see table). Mutual interference spiders disperse to about one spider/plant, appears to intensify with increase in prey and there is less chance that spiders will density. The m values for BPH densities encounter each other. of 10 and 30 were not significant, but m We observed some cannibalism, espe- was significantly large for the BPH cially in cages with three spiders. density of 60. This means that the spiders

Fluctuation of yellow stem borer (YSB) populations in Raichur, Karnataka, India

B. S. Nandihalli, B. V. Patil, and P. Hugar, Entomology Department, University of Agricultural Sciences, Raichur 584101, Karnataka, India

We used a modified Robinson model light trap with 160-W mercury lamp 1987-88 and 1988-89 to generate information on population fluctuations of YSB Scirpophaga incertulas (Walker) to use in the integrated pest management program.

Two peak activity periods were observed both years (see figure). The first

peak was Oct-Dec: moths caught per standard week ranged from 9 to 1,015 in 1987 and 4 to 559 moths in 1988.

caught ranged from 4 to 82 in 1988 and 26 to 1,042 in 1989. The insect was inactive Jun-Sep both years. More moths were caught Mar-May 1989 because canal water supply for the rice crop was low and most farmers did not apply plant protection measures.

These findings suggest that YSB counts to evaluate the need for crop protection measures should be made in the field the first week of Oct for wet season and during the first week of Mar for summer crops.

The second peak was Mar-May: moths

Population fluctuation of YSB Scirpophaga incertulas (Walker). Karnataka, India, 1987-89.

Toxicity of insecticides to mirid bug predator of rice brown planthopper

P. R. Srinivas and I. C. Pasalu, Entomology Department, Directorate of Rice Research, Rajendranagar, Hyderabad 500030, A.P., India

We tested 10 selected commercial formulations in the glasshouse for their toxicity to the predator Cyrtorhinus lividipennis (Reuter). Insecticide formulations were prepared with distilled water and sprayed (using a fine atomizer) to the runoff stage on potted 30-d-old TN1 plants. Control was distilled water only. Adult mirid bugs (30/treatment) were caged on the plants 4 h after spraying and mortality recorded 18 h later.

Synthetic pyrethroids cypermethrin, fluvalinate, and fenvalerate were highly toxic to the mirid bug (LC 50 values of

tively) (see table). Quinalphos also was toxic (0.008 LC 50 ). The insecticides methomyl and ethofenfox were relatively safe (LC 50 values of 0.024 and 0.041, respectively). The remaining insecticides exhibited moderate toxicity.

0.00036, 0.0045, and 0.0053, respec-

Toxicity of insecticides (LC 50 values) to mirid bug.

Insecticide LC 50 Range

Cypermethrin 0.00036*** 0.00039-0.00017 Fenvalerate 0.0053** 0.007 -0.004 Fluvalinate 0.0045** 0.006 -0.0033 BPMC 0.0073** 0.0094 -0.0057 Quinalphos 0.008** 0.010 -0.006 Chlorpyrifos 0.0095** 0.012 -0.008 Furathiocarb 0.01 17** 0.0152 -0.0091 Monocrotophos 0.0129** 0.0163 -0.0102 Methomyl 0.024* 0.0299 -0.0194 Ethofenprox 0.0406* 0.0456 -0.036

a * = log * 10 3 ; ** = log * l0 4 ; *** = log * 10 5

Feeding and food assimilation by two species of rice leaffolders (LF) on selected weed plants

M. L. P. Abenes and Z. R. Khan, IRRI-ICIPE Project, IRRI

Several weed plants present in the ricefields are reported to be alternate hosts for rice LF. We studied the feeding rates and

IRRN 15:3 (June 1990) 31

food assimilation of Cnaphalocrocis medinalis (Guenée) and Marasmia patnalis Bradley (Lepidoptera: Pyralidae) on 12 selected weed plants collected from ricefields and multiplied in the greenhouse.

The weed plants were Brachiaria mutica, Digitaria ciliaris, Dactyloctenium aegyptium, Echinochloa glabrescens. E. crus-galli, E. colona, Eleusine indica, Leptochloa chinensis, Leersia hexandra, Paspalum distichum, Panicum repens, and Paspalum conjugatum.

Third-instar larvae were starved but water satiated for 2 h and weighed individually (W 1 ). Leafcuts of weed plant, susceptible IR36, or resistant TKM6 rice (30- to 35-d-old) were offered in a no- choice test to individual LF larvae for 24 h. Larval weight (W 2 ) was recorded 2 h after the end of the feeding period. The setup was replicated 10 times.

Leaf area consumed was measured using a leaf area meter. Food assimilation was computed:

Food assimilation = W 1 ( C 1 - C 2 ) + ( W 2 - W 1 ) C 1

where W 1 and W 2 are initial and final weights of test insects and C 1 and C 2 initial and final weights of control insects.

C. medinalis larvae fed most on D. ciliaris, followed by E. glabrescens, P. conjugatum, and E. indica (see figure). Feeding on susceptible IR36 was lower than on D. ciliaris but comparable to feeding on TKM6, E. colona, E. crus- galli, L. chinensis, L. hexandra, and P. distichum. Feeding on B. mutica and P. repens was significantly lower than on either rice varieties as well as on most of the weeds tested.

Food assimilation by C. medinalis was highest on P. conjugatum, followed by E. glabrescens, D. ciliaris, D. aegyptium, and L. hexandra. Food assimilation on E. indica, E. crus-galli, P. distichum, and E. colona was similar to that on both susceptible IR36 and resistant TKM6. Food assimilation on P. repens was significantly lower than on the rice varieties and most of the weeds tested.

M. patnalis larvae fed most on susceptible IR36 and resistant TKM6. Feeding on L. hexandra and L. chinensis was comparable to feeding on IR36. Feeding on

32 IRRN 15:3 (June 1990)

Leaf area consumption and food assimilation by third-instar larvae of C. medinalis and M. patnalis on graminaceous weed plants and rice hosts.

the other weed plants tested was signifi- ties and significantly lower on L. hexan- cantly lower. dra and L. chinensis. There was either

Food assimilation by M. patnalis very low or no food assimilation on the larvae was highest on the two rice varie- other weeds.

Mass rearing of a mirid several 30-d-old TN1 rice plants infested

predator with five gravid BPH females (see figure). Plants, mirids, and BPH females

I. Manti, Sukarami Research Institute for Food are transferred into the oviposition cage Crops (SARIF), P.O. Box 34 Padang, West Plants are transferred to emerging cage Sumatra, Indonesia and B. M. Shepard, IRRI after 24 h. The door and top of the 45- ×

55- × 60-cm cage are made of glass; the Mirid predator Cyrtorhinus lividipennis three other sides, of fine nylon mesh. Reuter can be mass-reared on brown When the mirid eggs hatch, some planthopper (BPH) eggs, using TN1 rice gravid BPH females are added to provide plants. food for the mirids. Each cage will pro-

Adult mirids collected in the field are duce mirids of known age, which can be introduced into mylar cages containing used for experiments.

Procedure for mass-rearing C. lividipennis. DAI = days after mirid introduction.

Integrated pest management–weeds In preemergence treatments, thiobencarb (1.0 kg ai/ha) with one hand weeding resulted in the best weed kill and

Weed control in dry and seeded irrigated rice

wet

O. S. Kandasamy and SP. Palaniappan, Tamil Nadu Agricultural University, Coimbatore 641003. India

We evaluated 12 weed control treatments involving five herbicides applied preemergence and followed by (fb) hand weeding (HW) and applied early postemergence in combination with 2,4-D; and two hand weedings during Jun-Sep (kuruvai) and Oct-Feb (thaladi) at Aduthurai. In Jun, dry seeds of TKM9 (110 d duration) were sown on dry field; in Oct, sprouted seeds of IR20 (130 d

dicots (46%); in wet seeded rice, monocots predominated (79%). Irrespective of season, Echinochloa colona was the major grass species; Cyperus rotundus, the major sedge. Ludwigia adscendens was the major broadleaf. Marsilea quadrifolia (a fern) was also important.

Effect of weed control and seeding method on grain India.

in per-hectare yields of 4.9 t dry seeded rice and 4.6 t wet seeded rice (see table). Butachlor (1.5 kg ai/ha) with one hand weeding, and two hand weedings alone were equally effective. In postemergence treatments, no herbicide was effective in either dry or wet seeded rice.

yield and weed weight in direct seeded rice. Aduthurai,

Grain yield (t/ha) Weed weight (t/ha) Rate

Treatment (kg ai/ha) Dry Wet Dry Wet seeded seeded seeded

Unweeded control 2.4 2.7 2.4 1.7 Two hand weedings (15 & 30 DAS) 4.5 4.6 0.4 0.4

Preemergence duration) were sown on a puddled field. Thiobencarb fb HW The trial was laid out in a randomized Butachlor fb HW

block design with three replications. Fluchloralin fb HW Pendimethalin fb HW

1.0 1.5 1.0 1.5

Soil was clay loam. Preemergence Piperophos fb HW 1.5

herbicides were applied 5 d after seeding Early postemergence (DAS), early postemergence herbicides Thiobencarb + 2.4-D 1.0 + 1.0

were applied 15 DAS. Plots treated with Butachlor + 2,4-D 1.5 + 1.0

preemergence herbicides were hand 1.0 + 1.0

Pendimethalin + 2.4-D 1.5 + 1.0

4.9 4.6 4.2 4.2 4.0

3.9 3.6 3.5 3.5

4.6 4.5 4.5 4.2 4.0

3.8 4.0 3.9 3.9

0.4 0.5 0.5 0.7 0.8

0.9 0.9 0.9 0.9

0.4 0.5 0.5 0.5 0.6

0.6 0.6 0.7 0.7

weeded at 30 DAS. Plots with two hand Piperophos + 2.4-D 1.5 + 1.0 3.2 3.4 1.0 0.7

weedings were weeded 15 and 30 DAS. At 60 DAS , weed flora in dry seeded

LSD (0.05) for all plots, pre- 0.1 0.6 0.1 0.1 emergence and postemergence

LSD (0.05) between pre- 0.1 0.3 0.1 0.1 rice consisted of monocots (54%) and emergence and postemergence

Effect of time and number of weedings on direct seeded upland rice yields J. R. Patel, Indira Gandhi Agricultural University, Sub-Research Centre, Bangoli, Raipur, Madhya Pradesh 493225, India

In Bastar, India, 50% of the cultivable land, more than 40,000 ha, is upland, cultivated primarily by tribal farmers. Mean annual rainfall ranges from 1200 to 1600 mm. Southeast monsoon rains start in June and the rice crop is harvested at the end of the rainy season.

establishment method, and hand weeding is the only method of weed control.

We evaluated eight weed control methods during 1985-86 wet season in a randomized block design with three replications. Widely grown rice variety Culture 1 (90-95 d duration) was used.

Direct seeding is the preferred rice crop

Effect of hand weeding on grain yield, straw yield, weed dry weight, and control efficiency in direct seeded rainfed rice at Jagdalpur, Madhya Pradesh, India, 1985-86.

Grain Straw Weed Weed control Treatment yield yield dry weight efficiency

(t/ha) (t/ha) (t/ha) (%)

No weeding One hand weeding 20 DAS One hand weeding 40 DAS One hand weeding 60 DAS One hand weeding 80 DAS Two hand weedings 20 & 40 DAS Three hand weedings 20, 40, &

Four hand weedings 20, 40, 60 DAS

60, & 80 DAS LSD (0.05) CV (%)

0.2 0.9 1.2 0.7 0.4 1.4 2.0

2.3

0.3 12.2

0.5 1.6 2.1 1.5 1.1 2.4 3.5

3.9

0.5 10.2

2.8 1.2 1.7 2.1 1 .0 1 .0 0.7

0.3

0.4 11.8

48.0 57.3 40.3 29.3 64.0 75.3

80.0

With no weed control, yield was significantly. Straw yield, weed dry significantly lower (see table). When weight, and weed control efficiency weeding was delayed, yield decreased showed similar trends. proportionately, to the lowest with one At least two weedings at 20 and 40 d weeding 80 d after seeding (DAS). after emergence are needed to protect Weeding more than once improved yield yield potential.

IRRN 15:3 (June 1990) 33

seeded

Fluchloralin + 2,4-D

- -

- -

-

Weed composition in dry seeded wetland rice S. N. Jena, AICRIP Regional Research Station, Chiplima, Sambalpur, Orissa; and G. K. Patro, AICARP, OUAT, Bhubaneswar, Orissa, India

A major constraint on rice yields in Orissa State is high weed incidence. We identified the major weed flora and their composition in rainfed lowland rice during the 1987 wet season. All weeds in 0.25-m 2 samples from 12 wetland ricefields (two samples/field), were identified and the weed species found in all samples counted. All fields had been dry seeded.

Echinochloa colona was the dominant grassy weed found (see table). Sedges Cyperus iria, C. difformis, Fimbristylis miliacea, and Scirpus articulatus also had high incidence. Among the broadleaf weeds, Cyanotis cucullata and Ludwigia parviflora were high. Ipomoea aquatica, Hedyotis corymbosa, and Portulaca oleracea appeared at later crop growth stages.

First appearance and floristic composition of weeds in Orissa State, India. a

Botanical name First appearance

(DARE)

Cynodon dactylon (L.) Pers. Echinochloa colona (L.) Link Leptochloa chinensis (L.) Nees Ischaemum rugosum Salisb. Panicum repens L. Cyperus iria L. C. difformis L. C. rotundus L. C. imbricatus Retz Fimbristylis miliacea (L) Vahl Scirpus acutus Muhl. S. articulatus L. Aeschynamene indica L. Alternanthera sessilis (L.) R. Br. Cyanotis cucullata Kunth Hedyotis corymbosa (L.) Lam. Ipomea aquatica Forssk Limnophila indica (L.) Druce Ludwigia parviflora (L.) Roxb. Marsilea quadrifolia L. Manachoria vaginalis (Burm. f.) Presl. Portulaca oleracea L. Sesbania exaltata (Raf.) Cory. Sphenaclea zeylanica Gaertn.

Total

15 15 15 30 15 15 30 30 30 15 30 30 15 30 15 75 90 30 30 30 30

120 30 30

10.80 145.60 32.20 27.20 44.80

158.80 37.60 18.40 9.60

73.60 20.00 34.68 10.40

6.80 32.00

6.80 22.72 14.80 5.72

4.28 5.20

722.00

1.49 20.17

4.46 3.77 6.21

21.99 5.21 2.55 1.33

10.19 2.77 4.80 1.44 0.94 4.43

0.94 3.15 2.05 0.80

0.59 0.72

100.00

4.24 9.69 2.67 3.43 8.73 6.46 5.10 2.67 3.03 5.95 4.04 6.86 2.88 2.19 9.94 2.17 2.61 1.51 6.36

1.45 2.36 1.87 3.79

100.00

Weed composition b

30 DARE At harvest (165 DARE)

Plants/ % of Plants/ % of m 2 b population m 2 population

33.60 76.80 21.20 27.20 69.20 51.20 40.40 21.20 24.00 47.12 32.00 54.40 22.80 17.32 78.80 17.20 20.72 12.00 50.40

11.52 18.72 14.80 30.00

792.60

a DARE = days after rice emergence. b Av of 24 samples.

Farming systems Intercropping following rice

S. Muralikrishnasamy, M. N. Budhar, R. Rajendran, and A. A. Kareem, Tamil Nadu Rice Research Institute (TRRI), Aduthurai, Tamil Nadu, India

In the Cauvery Delta Zone, cotton Gossypium hirsutum or black gram Vigna mungo is grown in Jan-Feb following wet season rice. We evaluated cotton MCU7, soybean Glycine max (CO 1), and black gram (ADT4) as pure crops and cotton

intercropped with black gram or soybean, in a randomized block design with four replications.

with CEC 35 meq/100 g soil, 0.5% organic C, and 65% water-holding capacity. Spacing was 60 × 30 cm for cotton and 30 × 10 cm for black gram and soybean. In the intercrop treatments, two rows of cotton were sown at 45/75 × 30- cm spacing and two rows of the intercrop at 75- × 30-cm spacing.

Cotton was irrigated six times, with 30 cm water total; the pulse crops were

Soil was clay (fine Udic Chromusterts)

Yield and net return of sole crops and intercrops in rice fallow system. TRRI, Aduthurai, Tamil Nadu, India, 1988.

Yield a (t/ha) Yield Cultivation Net value b

Cotton Soybean Black gram ($/ha) cost return Treatment

($/ha) ($/ha)

Cotton Soybean Black gram Cotton + soybean Cotton + black gram

LSD (P = 0.05)

1.1

0.8 1.1

1.4

1.2 1.3

1.0

571 363 625 726

1052

264 112 131 343 336

307 251 494 383 716

18

a Mean of 4 replications. b Cotton, $519/t; soybean, $259/t; black gram, $481/t.

34 IRRN 15:3 (June 1990)

irrigated twice with 10 cm water total. The water table was 6.7 m deep during the cropping period.

Yield of cotton in the paired row intercrop with black gram equaled yield of cotton as a pure crop (see table). Cotton + black gram gave the highest net return.

Rice-based cropping systems for rainfed lowland conditions

R. B. Thakur, Rajendra Agricultural Univer- sity, Bihar, Pusa 848125, India

We studied the effect of seeding and fertilizer rates on the production potential of rice-based cropping systems under rainfed lowland conditions in 1988-89.

The soil was silty loam with pH 8.4, 0.62% organic C, and 278-39.2-140.2 kg available N, P 2 O 5 , and K 2 O per hectare.

Radha rice (35-d-old seedlings) was transplanted 15 Jul and harvested 10 Dec 1988. Gram C235, linseed Subhra, and lentil Pant 406 were broadcast 25 Nov in

- -

-

- -

- -

-

- -

-

-

-

- -

- -

-

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the standing rice crop at two seeding rates (normal and 50% higher than normal) with and without fertilizer. Fertilizer was broadcast 3 d before sowing the intercrop. The experiment was laid out in a randomized block design with four replications.

Rice yield was 3.8 t/ha. Yields of gram, linseed, and lentil ranged from 0.12 to 0.17, 0.45 to 0.68, and 0.16 to 0.29 t/ ha, respectively. (Lower yields of gram and linseed were due to a winter drought.)

Rice - linseed produced significantly higher rice equivalency yield than rice - gram and rice - lentil (see table). Linseed with fertilizer yielded significantly higher than other crops. The interaction between crops and seeding rates was not significant.

Production potential and economics of upland rice + pigeonpea S. S. Patra, Regional Research Station (RRS), Keonjhar 758002, Orissa, India

Upland rice + pigeonpea is the widely adopted mixed cropping system in

rice harvest reduces pigeonpea yields. Pigeonpea remains in the field 2 mo longer, and farmers lose interest in protecting a thinly populated crop that may not give an adequate return. Recom- mended seeding rates for single crop rice and pigeonpea are 100 and 20 kg/ha, respectively.

We evaluated proportions of rice and pigeonpea during 1985-87 wet season. The experiment was laid out in a randomized block design with three replications. Experimental crop schedules are given in the table.

Soil of the experimental site was sandy with pH 5.7, low available N (242 kg/ha) and P (8.0 kg/ha), and medium available K (97.0 kg/ha).

Rice cultivar Shankar (85 d duration) and pigeonpea UPAS 120 (145 d) were sown 21 Jun 1985, 24 Jun 1986, and 27 Jun 1987. Fertilizer was 60-13-25 kg NPK/ha for rice and 20-17.4-0 kg NPK/ha for pigeonpea.

Line sowing 2 rows of pigeonpea 50 cm apart after each 10 rows of rice 15 cm apart gave the highest return.

Keonjhar. But grazing by stray cattle after

Productivity of rice-based intercropping systems in Pusa, Bihar, India, 1988-89.

Treatment Grain yield (t/ha)

Rice Intercrop Rice yield Equivalence

Rice alone Rice + gram, normal seeding rate. no fertilizer (S 1 F 1 ) Rice + gram, normal seeding rate. fertilized a (S 1 F 2 ) Rice +gram + 150% seeding. no fertilizer (S 2 F 1 ) Rice + gram + 150% seeding, fertilized (S 2 F 2 ) Rice + linseed + S 1 F 1 Rice + linseed + S 1 F 2 Rice + linseed + S 2 F 1 Rice + linseed + S 2 F 2 Rice + lentil + S 1 F 1 Rice + lentil + S 1 F 2 Rice + lentil + S 2 F 1 Rice + lentil + S 2 F 2

LSD (0.05)

3.7 3.7 3.7 3.7 3.8 3.7 3.7 3.7 3.8 3.7 3.7 3.6 3.7 ns

0.1 0.2 0.1 0.2 0.4 0.6 0.6 0.7 0.2 0.2 0.2 0.3 0.1

3.7 4.1 4.2 4.1 4.2 4.5 4.9 4.8 5.1 4.3 4.2 4.2 4.4 0.4

a 20 kg N + 18 kg P/ha for gram and lentil, 30 kg N + 9 kg P/ha for linseed.

Yield and economics of rice + pigeonpea cropping system under different sowing methods and mixing proportions. a Orissa, India, 1985-87.

Treatment Yield Gross return Profit

Sowing Proportion (t/ha) ($/ha) ($/ha)

Rice 60% + 1.2 506.44 342.81 pigeonpea 40% 1.2

Rice 70% + 1.5 463.38 297.38 Rice and pigeonpea pigeonpea 30% 1.0 mixed and broadcast

Rice 80% + 1.6 444.88 276.56 pigeonpea 20% 0.9

Rice 60% (1.5 m broadcast 1.3 sown) + 565.81 399.75 pigeonpea 40% (2 rows 1.4 50 cm apart)

Rice broadcast Rice 70% (3.0 m broadcast 1.6 and pigeonpea sown) + 539.63 37 1.50 line dibbled pigeonpea 30% (2 rows 1.2

50 cm apart)

Rice 80% (4.5 m broadcast 1.9 sown) + 494.75 323.94 pigeonpea 20% (2 rows 1.0 50 cm apart)

Rice 60% (10 rows 15 cm 1.5

pigeonpea 40% (2 rows 1.5 50 cm apart)

Rice and pigeonpea Rice 70% (20 rows 15 cm 1.6 line sown apart) + 599.31 418.69

pigeonpea 30% (2 rows 1.3 50 cm apart)

Rice 80% (30 rows 2.1 15 cm apart) + 563.00 391.63 pigeonpea 20% (2 rows 1.1 50 cm apart)

apart) + 626.44 458.44

a Av of 2 yr.

IRRN 15:3 (June 1990) 35

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Rice-based intercropping systems for rainfed upland conditions of Chotanagpur plateau C. V. Singh, R. K. Singh, R. K. Tomar, V. S. Chauhan, and M. Variar, Central Rainfed Upland Rice Research Station, Hazaribag 825301, Bihar, India

In the upland area of Chotanagpur region (red lateritic, slopy), upland rice, ragi (minor millet), and pulses are grown in rotation with 1 yr fallow. Intercropping pulses or millets with upland rice could increase the cropping intensity of these areas.

We studied the feasibility of intercropping in red soils (pH 5.4, 0.39% organic C, and CEC 12.3 meg/100 g soil) during 1988 wet season.

Ragi (local), green gram (Sunayana), black gram (T-9), cowpea (Gomati), and red gram (BR65) were sown at 20-, 20-, 45-, 45-, and 75-cm row spacing, respectively, as sole crop and as intercrops.

Some transplanted rice- based cropping systems M. S. Sidhu, T. S. Sahota, B. D. Sharma, and B. K. Dhaliwal, Agronomy Department, Punjab Agricultural University, Ludhiana 141004, India

We evaluated some rice-based cropping systems involving cereals other than rice, legumes, oilseeds, and potato during 1987-88. The alluvial soil was calcare- ous, sandy loam with pH 8.1 and 0.28% organic C. All crops received recommended fertilizer except sunflower following potato.

rice - potato - transplanted winter maize (27.4 t/ha), followed by rice - potato - sunflower (21.8 t/ha) and rice - Indian rape - transplanted Swede rape - green gram (19 t/ha) (see table). Productivity of rice - wheat, the dominant cropping system in northern India, was lowest (8.8 t/ ha).

Maximum gross return was $2,970/ha with rice - potato - transplanted winter maize (more than 3 times the $953/ha return with rice - wheat).

36 IRRN 15:3 (June 1990)

Rice equivalent yield was highest with

Kalinga III rice was sown in 2:2 row ratio with ragi, 3:1 and 4:1 with red gram, and 2:1 with other crops.

The experiment was laid out in a randomized block design with four replications. N was applied as basal to pulses, at 20 kg N/ha. Rice was fertilized with 60 kg N and ragi with 40 kg N/ha. P and K at 17 kg/ha were applied as basal to all crops.

Rice alone yielded 22 t/ha (see table). In the intercrops, highest rice yield was in rice + red gram. Red gram produced the highest yield among the intercrops. Highest rice equivalent yield was with rice + red gram 4:1 ratio and lowest with rice + cowpea 2:l ratio. All combinations were efficient, with land equivalency ratios of more than one. Highest return was with rice + red gram.

Yield of rice and intercrops in Hazaribag, India, 1988 wet season.

Yield (t/ha) Rice Land Intercropping system equivalent Return equivalency

Rice Intercrop yield (t/ha) ($/ha) ratio

Rice + green gram 1.2 0.2 1.9 312 1.20 (2:1) Rice + black gram 1.3 0.2 1.9 321 1.27 (2:l) Rice + red gram 1.4 0.4 2.5 418 1.32 (3:1) Rice + red gram 1.6 0.4 2.6 438 1.36 (4:l) Rice + cowpea 0.9 0.3 1.7 289 1.12 (2:1) rice + ragi 1.0 1.1 1.7 29 1 1.02 (2:2) Rice alone 2.2 2.2 368 1.00

LSD (0.05) 0.2

Fertilizer costs were highest ($247/ha) The difference between returns from in rice - potato - transplanted winter fertilizer and total productivity is ascribed maize and lowest in rice - peas - green to the higher fertilizer requirements of gram ($126/ha). Fertilizer return was rice - potato - transplanted winter maize highest in rice - potato - sunflower and than in cropping systems involving lowest in rice - wheat. legumes and oilseeds.

Production and returns from some rice-based cropping systems in Punjab, India, 1987-88.

Total Rice Cost of Gross returns ($) equivalent fertilizer

Cropping system a yield yield ($/ha) Per Per $ (t/ha) (t/ha) ha fertilizer

Rice - wheat 8.4 8.8 163 953 5.85 (4.1) (4.3) Rice - winter maize 9.5 11.4 174 1229 7.06 (4.8) (4.7) Rice-peas-green gram 8.0 13.5 126 1462 11.61 (4.9) (1.7) (1.4) Rice - Swede rape - green gram 8.0 14.2 148 1579 10.66 (5.4) (1.4) (1.3) Rice - potato - transplanted winter maize 12.0 27.4 247 2970 12.03 (5.6) (20.5) (6.4) +20.5b

Rice - Indian rape - transplanted Swede rape 9.0 19.0 175 2052 11.73 (4.8) (1.8) (0.8)

- green gram (1.6)

Rice - potato - sunflower 6.2 21.8 162 2362 14.58 (4.9) (21.2) (1.3) +21.2 b

Rice - Indian rape - sunflower 8.4 15.0 138 1621 11.75 (5.1) (1.9) (1.4) a Figures in parentheses are yield (t/ha). In the first three systems, rice PR108 (145 d duration) was used; in the other systems, PRTB (125 d duration) was used. b Potato tubers.

grain

Water requirement for peanut following rice in Bangalore

K. Joseph and G. V. Havanagi, Agronomy Department, University of Agricultural Sciences, Bangalore, India

We studied the water requirement for peanut in summer rice fallows 1983 and 1984. One irrigation was given all treatments at planting. Treatments were irrigation at 40% soil moisture deficit at 30-cm soil depth, at flowering, pod formation, and pod filling; and at pod formation. The water table receded from 20.6 to 63.3 cm during the crop period.

Water use, yield, and yield attributes of peanut following rice under different irrigation levels.

Irrigation level a LSD Character (0.05)

T1 T3 T3

Plant height at 40.5 41.5 38.7 ns

Dry matter production at 9.3 10.2 9.9 ns

Test weight (g/100 kernels) 28.9 28.7 28.9 ns Shelling percentage 74.2 73.4 73.7 ns Pod yield (t/ha) 2.2 2.2 2.1 ns Water use efficiency 77.8 112.7 179.9 7.0 Water use (cm) 28.8 17.2 8.9

maturity (cm)

harvest (g/plant)

a T1= at 40% soil moisture deficit; T2 = at flowering, pod formation, pod filling; T3 = at pod formation.

Growth and yield attributes were additional irrigation (8.86 cm) only at statistically similar (see table). Water use pod formation. efficiency was significantly higher with

Rice variety to fit cropping patterns in Tripura, India S. K. Gupta and S. Laskar, ICAR Research Complex for N. E. H. Region, Tripura Centre, Lembucherra 799210, India

Rice variety Mahsuri is popular in Tripura but its 150-d duration delays sowing of succeeding crops potato, wheat, or mustard and preceding crops jute and rice.

We compared four 125-d duration rice varieties with Mahsuri during 1982 and 1983 wet seasons and 1983 and 1984 dry seasons. The experiment was laid out in a randomized block design with four replications.

Soil was loamy with pH 5.5,0.06% total N, 0.94% organic C, and CEC 9.97

Yield of rice cultivars to fit different cropping patterns In Tripura, India, 1982-84.

Yield (t/ha)

Variety Wet season Dry season

1982 1983 Mean Productivity 1983 1984 Mean Productivity (kg/d) (kg/d)

Mahsuri 2.6 2.3 2.4 16.3 2.5 2.7 2.6 16.5 Jaya 1.9 2.2 2.1 16.0 3 ..0 3.0 3.0 21.7 Vijaya 2.6 2.6 2.6 20.6 3.8 3.1 3.4 26.1 CR75-93 2.6 2.6 2.6 20.6 3.9 4.5 4.2 31.2 (Saberi) IR36 2.2 2.5 2.4 19.6 3.7 3.4 3.5 27.6

LSD a (0.05) ns ns ns 0.8 0.9 0.8

a ns - not significant

meq/100 g soil. Thirty-day-old seedlings Grain yields in the dry season differed were transplanted at 20- × 15-cm spacing: significantly. Highest yield was with fertilizer was 60-30-30 kg NPK/ha as Saberi (see table). urea, single superphosphate, and muriate Yields in the wet season did not differ of potash. significantly.

Relay cropping in upland rice fallows

T. Barik and K. C. Sahoo, Regional Research Station, Bhawanipatna, Kalahandi, Orissa 766001, India

We evaluated the effect of rice varieties Jajati and Assamchudi at three densities with six pulses as relay crops 1985-86 to 1987-88. The experiment was laid out in a split-plot design with three replications.

Soil was medium black, clayey, with medium fertility and pH 7.8.

Jajati rice yielded 0.2 t/ha more than local variety Assamchudi. Rice variety

and density had no significant effect on unusually lanky growth and poor stand, relay crop yield. which could be due to low temperatures.

Highest pulse yield was with lathyrus, Highest net profit was with bengal and lowest was with black gram (see gram, followed by lathyrus. improved table). Local field gram yielded higher pea, and local field pea. than improved field pea. Black gram had

Yield and return from pulses grown as relay crops following rice. Orissa, India, 1985-86 to 1987-88.

Cost of Net

(t/ha) ($) (d) Crop Variety Yield cultivation

($) Duration

Bengal gram OG 62 0.21 32.85 59.12 109 Lathyrus Local 0.22 21.90 41.75 104 Black gram T9 0.03 16.42 (-)7.23 92 Lentil T397 0.10 21.90 13.87 107 Improved field pea Rachna 0.15 32.85 31.97 102 Local field pea Local 0.19 27.37 27.52 101

IRRN 15:3 (June 1990) 37

profit/ha

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international rice research newsletter vol.15 no.3

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