Crop lmprovement 37 (2) : 93-99 (2010)

STRATEGIES TO IMPROVE POSTFLOWERING DROUGHTTOLERANCE IN FIAB'SORGHUM FOR PREDICTED CLIMATE

CHANGESCENARIOH.S. TALWAR-, PRABHAKAR, M. ELANGOVAN, ARUNA KUMABI, S.S. RAO.

J.S. MISHRAAND J.V. PATILDirectorate of Sorghum Research, Rajenderanagar, Hyderabad, SO0 OS0' ta lwa r @ so rg h um. res. n

ABSTRACTThe experiments were conducted.durlng rabi seasone of 2007-08, 2oog-09 and 2oog-10 to screen the promlsinggermplasm, advanced breedlng -llnes and landraces to iden ty the new sources

"nj1;i" """o"1"t"0 ,itl,posttlowering drought iolerance in sorghum. Th6 crop r""

"oiln under lrrigated

"na un.ii.ls"iJ condition toexamine the potential ot sorghum-genotypes to-.adapt 6 the posttlowering drought. lmproved sources (pEc 12, Ep87' EP 57' sLB 9, sLR and RSLG 2€2) for postftowering arougtrt iolerance have been identilied In terms of highergrain yield, biomass and gre€n lear area retentlon. sigrilficant-and positive relationships of spAD chlorophy meterreading (scMR) with total dry mater (R'i=0.67) and g-raln yietd 1*'=o.az1 suggests thii set-"iion-u"ing scMR witlhave 42-67'/' ptobabitity In selecting genotypes with trlgh"r tot"t dry .ater rnd grain yield. Most appropriate stageto screen for postflowering drought tolelance_on the ba-is of green Laf area tet

-ntion ist"y g;i iia'it) is arouna sodays after flowering. spectfic leaf welght (slw) increaseo stg-nifltanily unoer un-trrigJtea'ai'coifireo to irag"teoconditions in all the genotypes suggestlng increas€ In leatihickn;ss und6r molsture stress condiuons. posiiiverelationships between percent increase in SLw under stress conditions ano yietd components Indicatethat increasein leafthlckness is an lmportant adaptlve trait to postttowering drought. Thes" r""uitJ"on"iu j""l-ri"l-scr,,rn

""n o"used as a surogate measurement ot staygrean trait and increase ii stw unoer resiauai moisturelonoitions is apotential selectlon criteria tor postflowering drought tolerance in rabi sorghum.

Key words: Postflowering drought, SpAD chlorophy meter reading, speciric lea, weight, sorghum.

Sorghum (Sorghum bicolor(L ) Moench) ranks fifthamong the world's most important crops. lts currentworld production stands at 64.6 mil l ion tonnes while inIndia current production is 7.4 mil l ion tonnes. In India,sorghum is cultivated in both rainy and postrainy (rabi)season, mainly as a rainfed crop with about gS% of theproduction concentrated in Maharashtra, Karnataka andAndhra Pradesh. The national average productivity ofsorghum is very low (880 kg/ha). During postrainyseason, sorghum is cultivated predominanily on residualsoil moisture. Postflowering drought is a regular featureand is the major production constraint that adverselyaffects the crop growth and grain yield. with the threatof climate change looming large on the crop productivity,the most vulnerable regions of the world are the tropicsp a r t i c u l a r l y t h e s e m i - a r i d r e g i o n s w h e r e h i g h e rtemperature and increase in rainfal l variabi l i ty wouldaggravate the situation and would lead to frequentdroughts. Cl imate change impact on rabi sorghum isprojected to reduce the yield upto 7yo by 2020, upto

11o/o by 2050 and upto gO% by 20g0.

superior genetic resources are required to reducethe risk of losses in productivity due to postfloweringdrought . This requi res the ident i f icat ion of easi lymeasureable and cost effective traits related to terminaldrought tolerance. staygreen or delayed senescenceis a trait associated with postflowering droughttolerance(Subudh i e t a l . 2000) . Sorghum geno types w i thstaygreen trait continue to fil l their grain normally evenunder water def ic i t condi t ions (Borre l e t a l .2000) .Previously, superior sources of staygreen trait havebeen identified (Mahalaxmiand Bidinger zooz)and thistrait is currently used for erl identification in sorghum.S t a y - g r e e n h a s b e e n d e s c r i b e d a s t h e b e s tcharacterized trait contributing to the adaptation ofsorghum to terminal drought condit ions, i .e. condit ionsof water defici t that usually occur during and afterf l o w e r i n g ( R o s e n o w a n d C l a r k , 1 g g 1 ) . y e t , t h ephysiological mechanisms behind the expression of astay-green phenotype are s t i i l not c lear . Fur ther ,

H.S. Talwar et. al. [Vol. 37 No" 2

quan t i f i ca t ion o f s taygreen t ra i t requ i res e i the r

measurement of actual green leave area by destructive

sampl ing or est imat ion as length x breadth x 0 '70

( M a h a l i a x m i a n d B i d i n g e r 2 0 0 2 ) , w h i c h i s t i m e

consuming and expensive. Although, Mahaliaxmi and

Bidinger (2002) found a significant relationship between

visual rating of green leaf area retention with measured

green leaf area at maturi ty, while a previous study

indicated that these parameters are poorly correlated

(Bolanos and Edmeades 1996). These contradictory

resul ts might have been due to the involvement of

human error in al lott ing the score to the green leaf area

retention. Therefore, our research strategies are aimed

at identi fying the new sources of postf lowering drought

to le rance by eva lua t ing under s imu la ted d rough t

condit ions. The second objective to identi fy the cost

ef fect ive and easi ly measurable t ra i ts associated

p o s t f l o w e r i n g d r o u g h t t o l e r a n c e t o e s t a b l i s h t h e

selection cri teria.

MATERIAL AND METHODS

The exper iments were conduc ted dur ing rab i

seasons of 2007-08, 2008'09 and 2009-10 to screen

the promising germplasm, advanced breeding l ines and

landraces for postf lolering drought tolerance. During

these three seasons 90, 52 and 88 genotypes were

screened for postf lolering drought tolerance. During

2007-2008 , the s tud ies were conduc ted on ly a t

Hyderabad, while during other two seasons these were

conducted at two locations i .e Hyderabad and Solapur.

The experiments were sown in a spl i t-plot design with

three repl icat ions. Each plot consisted of 4 meter long

4 rows with row-to-row spacing of 0.60 m. A basal dose

of 20 kg ha'1 N and 20 kg ha-1 PrOu as di-ammoniumphosphate was broadcasted before final cultivation. The

seeds were hand sown and the f ield was irr igated to

saturate the soi l prof i le with water to ensure uniform

germination. The crop was thinned to two plants per hi l l

after 10 days of emergence and then to one plant per

hill after about a week to maintain plant-to-plant spacing

o f 0 .15 m. Around 20 days a f te r emergence , an

addit ional 20 kg ha-1 N as urea was side dressed and

f ie ld g iven i r r igat ion" Two water regimes (+ and -

irr igation during terminal growth period) were the main

plots and genotypes were the subplots. Crop was kept

free from water stress under + irr igation treatment,

whereas the crop under - irrigation treatment was kept

free from water stress t i l l ini t iat ion of f lowering and

therea f te r i r r i ga t ion was w i thhe ld up to matu r i t y .

Recommended packages of practices were followed.

The crop was protected from leaf feeding insects and

stem borer with appropriate insecticides. During these

three seasons, rain did not inter{ere in the postflowering

drought treatment. Required obseruations (Plant height

and lea f numbers a t f l ower ing and phys io log ica l

maturi ty, green leaf area estimation at f lowering, 15, 30

and 45 days after f lowering) and yield components(biomass, fodder weight, panicle weight and grain yield)

were recorded at physiological maturity.

Separate trials were conducted to identify the traitsassociated with postf lowering drought tolerance. In

o rder to s imp l i f y the measurement techn ique o f

staygreen trait and improve the repeatability, SPAD

chlorophyll meter readings (SCMR)were used to identify

the genotypes with staygreen trait having improved

tolerance to postf lowering drought in terms of yield

components. SCMR were recorded at 15 days interval

after flowering til l physiological maturity on second f ully

expanded leaf from the top. The reading was recordedat five spots to cover the entire leaf from the base to

top. Adequate care was taken to avoid midrib region.

Plant growth analysis was performed at 20 daysinterval days after imposing the stress t i l l physiological

maturity. Plant sample of 1.2 m2 area was collected by

cutting the plants from the ground level. Plant pafts were

separated into leaves, stem and panicles and were driedin oven at 80 oC for 48 hours to record the oven dry

weight, Leaf area and plant height were recorded on

five representative plants in each plot the two middle

rows. Leaf area was estimated by measuring the length

and breadth of top six leaves and calculated by the

formula, length x breadth x 0.71. Specif ic leaf weight

was calculated as the ratio of leaf weight to leaf area.

At maturity plants were harvested from 10.8 m2 (3m

x 6 rows of 0.60 m row-to-row spacing) area. The dry

weights of vegetative parts and panicles were recorded

after drying the samples in a hot air oven lor 48 hours

at 80"C. The panicles were threshed and grain yield

was recorded.

The data collected were subjected to ANOVA using

Sfafisfx 8.1 software for assessing the genotypic

interaction with postflowering moisture stress.

RESULTS AND DISCUSSION

Evaluation of advanced breeding rines, rand racesand promising lines for postflowering drought toleranceindicated the ex is tence of s ign i f icant genotypicvariations for yield parameters (Biomass and grain yield)at both the locations i.e. Hyderabad and solapur (Table1). Genotypic variations were clearly evident for biomassaccumulation, grain yield and percent of green leaf arearetained (GLAR) at physiological maturity as comparedthat at flowering under both stress and non-stressconditions. The data clearly indicates that biomass andgrain yield reduced at solapur than Hyderabad during2008-09 and 2009-10. This is because more severityof postflowering drought at solapur as compared thanHyderabad. The reduction in the reaf gas exchangeunder drought has been reported (Khofova et at.2oog),and this might have led to lower biomass accumulationand grain yield. Most of lines which performed betteralso retained the more green area at the physiologicalmaturity. This confirms the earlier observation thatdelayed senescence is a useful trait which associated

December,2010] Drought tolerance in rabi sorghum 95

with postffowering drought tolerance (Talwar et al. zo0g).A severe drought stress during post-flowering stageslike anthesis or post anthesis causes loss of cnlorophyll,cell electrolyte leakage, flag leaf yellowing and grainpre-maturation (Beltrano and Ronco 2009, Talwar efal. 2009). During last three seasons, the s,orghumgenotypes like pEC 17, Ep 97, Ep 57, SLB g, SLR 25and RSLG 262 have been identified as new sourceshaving improved postfrowering drought torerance basedon the yield components and green leave area retentionat the physiological maturity (Table 1).

The strong rerationship between drought sensitivityindex and percent change in spAD chrorophyil meterreading (scMR) under water deficit conditions inoicatesthat higher chlorophyl l concentrat ion is v i tar foradap ta t i on to wa te r de f i c i t cond i t i ons du r ingpostflowering growth period (Fig. 1a). significant andpositive relationships of scMR with total dry mater (R2=0.67) and grain yield (R2=0.42) suggests that selectionusing scMR wiil have 42-67% probabirity in serectinggenotypes with higher totar dry mater and grSin yierd(Fig. 1b & c). This indicates that sorghum genotypeswith delayed or non-senescent traits continue to filltheir

Table 1' Evaluatlon ot Eorghlm g€nqtypes tor post-floworlng drought tol€rancr grown at Hyderabad and solapur durlng 2002.

Season No ofgenotypes

Location Parameter Range Top flve genotypes performedunder postflowerlng drought

2007-08 Hyderabad

NA

2008-09 52

Solapur

Hyderabad

Hyderabad

Solapur

Biomass ( g/mr)Grain yield ( g/mr)Green leaf arearetention

Biomass (/m1Grain yield (g/mr)

440 * 27.1132 x,21.0

NA

NANA

3 1 6 - 5 9 7

88 - 245

NA

NA

NA

NA444 - 2282153 - 471

437 - 1172

534-1 98854.9 -238

123-1045

475 -1223

199 - 42315.7 - 31.2

503 -1091

109 - 36910.0 - 52.0

52 Solapur

Green leaf area retention NABiomass (g/mt) 1567 t 006Grain yield (g/mr) 01 4 * 17.5Green leaf area 944*121.3retention

Biomass (dmr) 1394 t 130.0Grain yield (g/mr)) 143 119.6Green leaf area 4gg t 20g.sretention

Biomass (g/mt) 984 *,72.6Grain yield ( g/m2) 308 r 11.9Green leaf area 21.7 x, O.g0retention

Biomass (g/mt) 737 *,4Z.TGrain yield (g/mz) 248 * 10.9Green leaf area 25.9 + 4.Sretention

SLB 9, SLR 25, pVK kranthi,

.RSLG 262 |

NA

EP 87, PEC 17, RSLG 262,PEC 16, PEC 23

EP 87, PEC 17, BSI_G 262,PEC7, SLR 25

EP 93, PEC 16, EP57, EP 87,PEC 17EP

127 ,EP 14 ,EP57 , EP 97 ,PEC 17

2009-1 0

96

C = 0.71

H.S. Talwar et. al"

b R2 = 0.67

[Vol. 37 No. 2

rt = 0.42

trE t r t r

E

SCMR

sensit ivi ty index (a) and relat ionships of SCMRin 20 genotypes grown under + and - irr igation

160

ct

Ect)g.9 200

c(!

o

ct

Eg

b 600

G'El' 400

lC

(E

€ zoo

x

{ rzo

=,='6

806'o

E )r 4 0o

o

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

% decrease in SCMR in water defiicit SCMR

Fig. 1. Relat ionship between change in SCMR due to water defici t condit ions with(SPAD chlorophyll meter reading) with total dry matter (b) and grain yield (c)treatments during post flowering growth period.

60

grain normally even under l imited water or moisture

stress conditions during postflowering growth period

(Borrel l et a\.2000). Delayed senescence and yield

components are posit ively associated under waterlimited environments as reported in a range of studiesconducted in lndia(Borrell etal.2OO1; Reddy etal.2007)

and abroad (Borrell et a\.2000). Staygreen genotypes

have been shown to maintain higher leaf-nitrogenconcentrat ions during grain f i l l ing (Borrel l et a\.2001 ),prod uce sign if icantly greater total biom ass after anthesisand grain yields under postf lowering drought stress thanthe senescent hybrids (Borrell et a\.2000). Delaying of

leaf senescence enhances both radiation use efficiencyand transpiration use efficiency resulting in higher yield(Richard 2006). Further to improve the repeatability ofresults, our results suggested that most appropriatestage to identify genotypes on the basis of green leafarea retention with improved biomass and grain yield

under postflowering drought tolerance is around 30 daysafter flowering (Table 2).

Another leaf trait which gets affected under water

deficit condition was found to be specific leaf weight,

SLW (the ratio of leaf weight to leaf area). SLW differs

signif icantly among the genotypes under both the

treatments of water regimes (Table 3). There was

significant increase in SLW under stress conditions ascompared to that under non-stress condit ions. This

suggests that leaf thickened under moisture stressconditions. SLW is reported to be related to droughttolerance in several crops and has been suggested as

a selection criterion for breeding programs targeting lowrainfallareas. Genotypes with a high specific leaf weighthave leaves with a small surface area to volume ratio,in other words, thick leaves, which is an advantage inusing water efficiently. Significant genotypic variationswere recorded in the percent increase in SLW understress conditions in six genotypes evaluated (Table 3).Increase in leaf thickening (decrease in specif ic leafarea or increase in SLW) under drought conditions have

been reported in amaranths (Liu and Stutzel 2004),pearlmil let (Kholova et a\.2009) and sugarbeet (Ober

et a\.2005). The range of increase in SLW under stress

Tablo 2. Slgnlllcanc6 lgvels ot correlallon coetllclenla botwe€n the green lgat area reienlion durlng dlfferent growth alagoa andyleld compon€nts (blomas8 and graln yleld).

Yield Water Green leaf area retention at

Component Regime Flowering 1O DAF 27 DAF 40 DAF 48 DAF

Biomass

Biomass

Grain yield

Grain yield

No stressStressNo stressStress

0.53"

0.46'

0 .40

0 .49* '

0 .53* '

0 .46 '

0 .40

0.49"

0.56"

0.59"

0.4.8"

0.56"

0 .49 . '

0 .48 '

0 .31

0 .38

0.42

0.45'

0 .27

0.28

DAF= days after flowering.

December,2010] Drought tolerance in rabi sorghum 97

conditions as compared to that under non stressconditions was 48.2 to 133.4 % (Table 3). The maximumlncrease in sLW was recorded in 'M 3s-1'and minimumrn 'csv 18'. Genotypic variations in the increase in reafthickening under moisture stress conditions have been:eponed (Kholova et al.2oog) and it was more in tolerant:han sensi t ive genotypes in pearrmi i let . posi t ivererationships between increase in sLW under stressconditions with total dry matter (R2 =e.46), panicle weight(R2=0.80) and grain yield (R2=0.71) were recorded(Figure 2). comparatively, the relationship with fodderiveight is weaker; this may be due to the low biomasspartitioning to grain yield in 'csv 1g'. These refationshipsbetween increase in sLW under stress conditions and5'ield components indicate that increase in leaf thicknessis an important adaptive trait to drought and can be a

potential selection criterion for the postfrowering droughttolerance in rabi sorghum.

REFERENCESBeltrano, J. and Ronco, M. G (2OOg). lmproved tolerance ofwheat prants (Triticum aestivum t-.i to orougnistress

and rewatering by the arbuscular mycorrhiial fungusGlomuscraroideum: Etfect on growth and ceil membranestabirity. Brazirian Journar of-prant physi;to;i zn: ze-37.

Bolafios, J. and Edmeades, G. O. (1996). The importance ofthe anthesis'sirking intervar in breeding for droughttolerance in tropicar maize. Fierd crops-Research 4g:65-80.

Borrell, A. K, Hammer, G L. and Dougtas A. C. L. (2000).Does maintaining green leaf arealn sorghum improueyield under drought? r. Leaf growth and- s"n.rcence.Crop Sci. 40: 102*87.

Table 3: variation in % green leaf area.retentlon (GLAR) at physrorogrcar maturity, bromass accumuFll-o__n during postfrowerrngff:fffi::'"ffi[f,lTt"ffl:tt

in o senoivp"l' s'o*n undir trrtsated (rn1 ana uniirrsated (uNrR) condi*ons durinsGenotype % GLAR by top six leaves

as that at flowerlng atphystotoglcal maturlty

% Blomass accumulatlondurlng postflowerlng

growth perlod

Speclfic leaf wetght(g/m.)

I R UNIR UNIR' csv 216 R''csv 1g '' M 3 5 - 1 ''sPV 1626''296 B''c 43'Ir/ean

SEmt

CVo/"

UNIR37.0

44.2

57.0

22.9

71 .0

64.8

49.6

6.3

5.7

30.2

8 .8

38.6

1 9 . 3

18.2

109

97158

102

184

126

129 .8

48

73

144

85

1 1 1

97

93.3

1 1 . 6 3

8.527.66

8.20

7.64

7.03

8.5

19 .67

12.63

17 ,88

13.17

8.9010.67

13 .85.227.2

32.328.2

1 .65

17 .6

R'= 0.804

I 50 100 160Toincrease ln speclf lc leaf wclgl i i '

R2= 0.710

60 100 150

350

300

f 250E

9eooT'c)'f rsoau

o 1oo

360

E sooo)

:25oCD

= 200.l)

.E rooEoe 1oo

60

0

I 'Eo 800t_o

v

F 600E

t-E

5 400oF

200

0 50 100 tsoo/oincreasc in Speci f ic lcaf wcig l r tIncr.s.c In sp.clflc t..rrrclchtFlg 2' R€lationship ol p€rcent increase jn- specitic leaf weighl under moistur€

-slress al,ith.yield componenb (totaldry maner, lodderffl?iX'.ffil!':,X?rf"jsht

and grain vield) in e g"";d,pl" si"r"'iid:,'rr,,sateo 1rF1 and un-irrrsat€d (uNrR) 6nditions dudno

H.S. Talwar et. al. [Vol. 37 No. 298

Borrell,A. K., Hammer, G L. and van Oosterom, E' J' (2001)'

Staygreen:aconsequenceof theba|ancebetween'upp tyanddemandofn i t rogendur inggra in f i | | i ng?Annals of Apptied Biology 138: 91'5'

. /ixb.oxfordjou rnals. org/)

Liu, F. and Sttltzel, H. (2004). Biomass partitioning, specificleaf area, and water use efficiency of vegetable amaranth(Amaranthus spp.) in response to drought stress'Scientia Horticulturae 1O2 (2): 15'27 '

Mahalakshmi, V. and Bidinger, F. R. (2002). Evaluation ofStaygreenSorghumGermp|asm|inesat|CR|SAT.CropSci.42:965-74.

Ober, E. S., Bloa, M. le., Clark, C. J. A', Royal, A', Jaggard'K. W. and Pidgeon, J . D. (2005) ' Evaluat ion of

physio |ogica| t ra i tsas indi rectse|ect ioncr i ter ia fordrought tolerance in sugar beet. Fietd Crops Research

91 (2-3): 231-41

Richard, R. A, (2006). Physiologicaltraits used in the breedingof new cult ivars for water-scarce environments.Ag ric u tt u rat W ate r M an ag e ment 80( 1'3\: 1 97 -21 1

Reddy, B. V. S., Ramaiah, 8., Ashok Kumar' A' and Reddy'i. S. (zOOz). Evaluation of Sorghum genotypes for

staygreen trait and grain yield. An openAccess Journalpublished bY lCRlSAf 3(1): 1-4.

Subudhi, P. K., Rosenow, D. T. and Nguyen, H'T' (2000)'

Quantitative trait loci for the stay green trait in sorghum(Sorghum bicolor L. Moench): consistelgy acrossgen"lic background and environments' Iheor' Appl

Genet 101 (5-6): 733-41 .

Talwar, H.S., Surwenshi,A. and Seetharama, N' (2009)' Use

of SPAD chlorophyll meter to screen sorghum (Sorghu m

bicotol1lines for postflowering drought tolerance ' Indian

Journal of Agricuttural SciencesTg (11: 432'37 '