PART A: DURUM WHEAT. 3.1A Introduction

Transcription

1 PART A: DURUM WHEAT 3.1A Introduction Global area under durum is about 17 million hectares and production is about 25 million metric tones. India is one of the major durum producers and almost entire produce of 2.5 million tons which is used to meet domestic requirements (Jag Shoran et al., 2004). In Central and Peninsular Zone of India, durum wheat is traditionally cultivated under residual soil moisture conditions. Even with changed and improved irrigation scenario in these regions, water is still a major limiting factor for wheat production. In majority of cases wheat crop receives 2-4 irrigations in Central and Peninsular Zone (Pandey, 2004). Breeding strategy for identifying genotypes for these situations is becoming a major challenge for all breeders in Central and Peninsular India. Several morphophysiological traits have been proposed as screening criteria for drought tolerance (Turner, 1997) such as relative water content (RWC). Transpiration efficiency (TE: the ratio of dry matter produced to water transpired) is an interesting attribute for growth in dry areas. The use of carbon isotope discrimination ( ) as a related criterion which affords an easy way of screening for TE.The negative relationship between and TE was established firstly by Farquhar and Richards (1984) and confirmed by other workers, who then proposed as an indirect selection criterion for TE (Condon et al., 1987; Ehdaie and Waines, 1993; Acevedo, 1993) During photosynthesis, plants discriminate against the heavy isotope of carbon ( 13 C) which leads to depletion of the plant dry matter in 13 C.Carbon isotope discrimination is a measure of 13 C/ 12 C ratio in plant dry matter compared with the value of the same ratio in atmosphere (Farquhar and Richards 1984). In C 3 Species, including bread wheat and barley, was found to be positively correlated with C i /C a (i.e., the ratio of internal leaf CO 2 concentration to ambient CO 2 concentration) and negatively associated with TE, (Farquhar and Richards 1984, Ehdaie et al., 1991, Johnson and Bassett1991, Read et al., 1991, Acevedo 1993). Values appear to provide a useful integration of TE of C 3 crop species, and therefore have been proposed as potential criterion for TE (Farquhar et al., 1989). Carbon isotope analysis, using mass spectrometry, is however very expensive, especially for the screening of large collections of genetic resources. Attempts have 53

2 been made to develop alternative screening methods. Ash content (m a ) and dry mass per unit of leaf area (LDM) have been proposed as surrogates for (Masle et al., 1992; Wright et al., 1993; Voltas et al., 1998) and as an alternative selection criterion for TE and yield. Other morphological traits associated with yield, such as grain number and HI, can be used in visual selection of breeding lines. Several workers have shown a clear association of CTD with yield in both warm and temperate environments. CTD shows high genetic correlation with yield and high values of proportion of direct response to selection (Reynolds et al., 1998), indicating that the trait is heritable and therefore amenable to early generation selection. Since an integrated CTD value can be measured almost instantaneously on scores of plants in a small breeding plot (thus reducing error), work has been conducted to evaluate its potential as an indirect selection criterion for genetic gains in yield. The objectives of the present study were to identify traits associated with yield. The potential value of, m a and CTD as an indirect selection criterion for yield was identified. On the basis of this criterion selections were made to increase the grain yield under water stress condition. 3.2 A Materials and Methods A Selection of wheat varieties and procurement of seed Twenty semi-dwarf durum wheat genotypes including released varieties were selected (Table 3.1A). The experiment was conducted for two consecutive years and for the confirmation of the results. 54

3 Table3.1 A: List of durum wheat genotypes included in and trial. Sr.No. Name of the genotype Source Suitable for 1 HI 8627 IARI RRS Indore irrigated 2 UAS 405 UAS Dharwad Irrigated 3 UAS 401 UAS Dharwad Irrigated 4 HI 8666 IARI RRS Indore Rainfed 5 HI 8498 IARI RRS Indore Irrigated 6 MACS 2694 ARI,Pune Irrigated 7 NIDW 295 ARS Niphad Irrigated 8 MACS 3618 ARI,Pune Irrigated 9 MACS 3125 ARI,Pune irrigated 10 MACS 3572 ARI,Pune irrigated 11 MACS 3518 ARI,Pune irrigated 12 HI 8641 IARI RRS Indore irrigated 13 NIDW 350 ARS Niphad irrigated 14 DD 07 DWR Karnal irrigated 15 MACS 3640 ARI,Pune irrigated 16 MACS 2846 ARI,Pune irrigated 17 HD 4672 IARI, New delhi rainfed 18 RKD 111 KOTA,Rajasthan irrigated 19 UAS 404 UAS Dharwad irrigated 20 MACS 3571 ARI,Pune irrigated 55

4 3.2.2A Experimental Trials Trials were conducted at the Experimental Farm of Agharkar Research Institute, located at Hol Distt. Pune, India (18.04º N, 74.21º E and m above sea level) during and cropping seasons. The experiment was conducted in a randomized block design (RBD) with3 replications and 3 treatments. The treatments were Residual Soil Moisture Stress (RSMS), Post-Anthesis Water Stress (PAWS) and Well-Watered (WW) conditions. Seeds were sown in 4m x 6 rows spaced 23 cm apart (260 seeds/m 2 ). Fertilizer application (N P K) was done as per recommended doses (60:30:40) for RSMS, (80:40:40) for PAWS and (100:50:40) for WW conditions. Nitrogen application in PAWS & WW was given in two times i.e., half at sowing time and half 25 days after sowing at first irrigation A Climatic conditions During and total precipitation received was mm and mm respectively (Table 3.2A). Table 3.2 A. Rainfall and irrigation during crop seasons ( to ) Rainfall/ Irrigation (mm) Year March February January December November May to October (Irrigation) Total Rain (Irrigation) RSMS WW (Irrigation) PAWS Crop was flood irrigated. First irrigation was given immediately after sowing to ensure proper germination of experiment. No irrigation was given to RSMS; three irrigations were given to PAWS (180 mm) and five irrigations to WW (300mm) A Observations Observations were recorded as follows: A. Agronomical traits Data on agronomical traits were recorded as mentioned in chapter 2, section

5 B Physiological traits Carbon isotope discrimination Ash content Canopy temperature depression For physiological traits, observations on CID and ash content were recorded as mentioned in chapter 2, section C. Canopy Temperature Depression (CTD) Canopy temperature depression data was recorded for 20 genotypes at anthesis (CTD a ) and at maturity (CTD m ) using a portable infrared thermometer during full sunshine hours (Model AG-42, Telatemp Corporation, Fullerton, CA). 3.3A Statistical analysis Data were analyzed using Agrobase 99 software for all the traits where replicated trial data was recorded. Combined ANOVA was done to estimate G X E interactions over environments and compare differences between environments. For CID analysis, data from individual samples were analyzed and SD was calculated. Phenotypic correlations were estimated (r) to determine the relationship between traits and grain yield. 3.4A Results Significant differences were found for grain yield between the three water treatments. The highest grain yield were recorded under WW regime, followed by PAWS and RSMS.Average grain yield was 4.58, 3.65 and 2.34 t/ha, for and 4.532, and t/ha for season, respectively. Genotypes x Treatment (Environment) interaction was highly significant for grain yield, harvest index, plantlet leaf ash (m a L p ), leaf ash at boot stage (m a L b ),leaf ash at anthesis (m a L a ) grain ash (m a G m ), grain Carbon isotope discrimination ( G m ) except for biomass and leaf carbon isotope discrimination at anthesis ( L a ) in both the seasons(table3.3). 57

6 Table 3.3 A. MS of combined ANOVA for grain yield, biomass, harvest index and ash content ( ) and ( ). Season Source of Variation d.f. Yield Biomass HI m a L p m a L b m a L a m a G m L a G m Treatments (T) *** *** *** *** 19.03ns *** 1.49 *** *** 26.6 *** Genotype (G) * 5.70 ** ** 1.93ns 7.46ns 4.79 * 0.13 *** * *** *** G x T *** *** *** 1.76 *** 5.38 *** 2.34 *** 0.05 *** *** Treatments (T) *** *** *** *** *** *** 0.98 *** *** *** Genotype (G) G x T ns *** 2.96 *** 4.47ns 1.851** ns ns 7.839ns 3.768ns *** ** *** *** *** 0.35 *** *** *** *, **, ***, significant at p=<0.05, 0.0 and respectively. ns = non significant m a G m, m a L p, m a L b m a L a m a L m, magm: Ash content in grain at maturity, plantlet and flag leaf at boot stage, anthesis and grain respectively; L a and G m: CID at flag leaf at anthesis and grain, respectively. HI = Harvest Index 58

7 Table 3.4 A: Ash content, biomass, yield, CID and CTD under the different water regimes in ( ) and ( ) season. RSMS PAWS WW Season Trait Mean S.D. Mean S.D. Mean S.D. F value L a ( ) G m ( ) MaLp (%) m a L b (%) m a L a (%) CTDb CTDa m a G m (%) ** Yield (T/ha) Biomass (T/ha) Harvest Index (%) b a a *** b a a *** b a a *** a a a *** a a b *** a a a *** b a a ns b b a *** b a a *** b a a *** c b a *** b a b *** b a a *** a a a *** a b c *** b b a *** b a a *** c b a *** a b a ** a a b *** *** Significant at p=< ; RSMS: Residual Soil Moisture Stress, PAWS: Post Anthesis Water Stress, WW: Well Watered. L p and L a and G m: Carbon isotope discrimination in plantlet, flag leaf at anthesis and grain at maturity, respectively MaGm, m al p, m al b m al a m al m: Ash content in grain at maturity, plantlet and flag leaf at boot stage, anthesis and maturity respectively. Mean values on same line without a common letter are significantly different (P< 0.05) according to the Duncan comparison test.$ = values from pooled samples, analyzed at UAS Bangalore; # = values from individual plots, analyzed at Siberdorf lab CTD a, CTD b canopy temperature depressin at boot and anthesis, mean values on same line without a common letter are significantly different (P< 0.05) according to the Duncan comparison test Highest grain ash values were found in WW (1.73, 1.53) followed by PAWS (1.58, 1.52) and RSMS (1.41, 1.31) in both the seasons respectively. For plantlet leaf ash highest values were recorded in RSMS (16.07, 15.85) followed by PAWS (15.42, 15.43) and WW condition (12.54, 15.14) in respective seasons. Similar trend was 59

8 obtained during season. Higher leaf ash content at anthesis was recorded for WW (12.58, 12.06) followed by PAWS (12.31, 11.19) and RSMS (9.77, 8.83) during both the seasons (table 3.4A) A Effect of water regime on grain yield, carbon isotope discrimination and ash content Significant differences in the treatments were observed between grain yield and ash content due to water regimes. Highest grain yield was observed under WW conditions.similarly highest values for leaf ash at anthesis and grain ash were recorded under WW followed by PAWS and RSMS conditions. Grain yield, biomass and ash content showed highest values under WW condition suggesting that high yield was associated with low transpiration efficiency. Similar results were obtained for previous season (Misra et al., 2006).On the contrary plantlet leaf ash showed highest values under RSMS followed by PAWS and WW condition (Table3.4A). Under RSMS, PAWS and WW regimes, grain yield showed significant correlation with BIOM (0.445 ***, ***, *** ) and (0.788 ***, ***, *** ) for and season respectively. Grain yield also showed significant correlation with HI under these three environments (0.748 ***, ***, *** ) and (0.530 ***, ***, *** ) for and season respectively (Table 3.5A). For carbon isotope discrimination, G m showed highest value under PAWS (17.14) condition in however, in season under WW condition G m showed highest value (17.59). Canopy temperature depression at boot stage (CTD b ) showed highest value under WW (4.23) condition followed by PAWS (2.67) and RSMS (1.70) condition. Canopy temperature depression at anthesis stage (CTD a ) showed highest value under PAWS (4.48) followed by RSMS (2.88) and WW (2.82) environment. In season DF and DM showed significant negative correlation with yield under WW condition ( *** and *** ) respectively whereas in season DF and DM showed significant negative correlation under PAWS condition ( *** and *** ) respectively (Table 3.5A). 60

9 TABLE3.5A. Correlation between phenological and morphological characters and yield and BM HI DF DM TGW HT CTD a CTD b RSMS PAWS WW *** *** *** *** ** *** ** ** ** *** *** ** *** *** * ** ** *** *** *** ** ** ** *** *** * RWC m a L p m a L b m a L a m a L m m a G m L a G m RSMS PAWS WW *** *** * *** ** *** ** *** ** * ** ** *** * * *** * *, *** and *** Significant at p=<0.05, 0.01, RSMS-Residual Soil moisture stress, PAWS-post anthesis water stress, WW-Well watered regime. BM: Biomass, HI: Harvest index, DF: Days to flower, DM: Days to Maturity, TGW: Thousand Grain Weight and HT: Plant height, CTD a Canopy temperature depression at anthesis, CTDb : Canopy temperature depression at boot stage, RWC: Relative water content. L p and L a and G m: Carbon isotope discrimination in plantlet, flag leaf at anthesis and grain filling stage, respectively MaGm, m a L p, m a L b m a L a m a L m : Ash content in grain at maturity, plantlet and flag leaf at boot stage and anthesis and maturity, respectively; - 61

10 3.4.2A Relationship between grain yield, carbon isotope discrimination, canopy temperature depression and ash content under residual soil moisture stress condition Under RSMS environment, higher values of ash at plantlet stage were recorded in both seasons. Grain yield showed significant positive correlation with biomass and HI (table 3.5A).Non significant negative correlation ( ***,-0.066) was observed between grain yield and canopy temperature depression at anthesis (CTD a) in season. For grain ash content grain yield showed negative significant correlation in the both the seasons. No correlation was observed between m a L p and m a L b under both the seasons. In grain yield showed significant correlation with leaf ash at anthesis (0.235 *** ) whereas in season no correlation was observed between grain yield and leaf ash at anthesis (m a L a ). Under RSMS condition grain yield showed significant positive correlation(0.447 *** and *** ) with leaf carbon isotope discrimination ( L a ) and grain carbon isotope discrimination ( G m ) respectively in season.in season there is a lack of correlation between grain yield, L a and G m.(table3.5a). Grain carbon isotope discrimination showed significant correlation (0.386 ***, *** ) for leaf ash content at anthesis (m a L a ) in both the seasons. Grain carbon isotope discrimination ( G m ) also showed significant negative correlation ( ***, ) for canopy temperature depression at anthesis (CTD a) and significant positive correlation (0.386 ***, *** ) for leaf carbon isotope discrimination ( L a ) in both seasons respectively (table 3.6A) Leaf carbon isotope discrimination at anthesis showed significant correlation (0.303*, 0.311*) for leaf ash content at anthesis (m a L a ) in both the seasons. It also showed significant correlation (0.475 *** ) for leaf ash content at maturity (m a L m ) in season and significant negative correlation ( ***,-0.024) for canopy temperature depression at anthesis (CTD a ) in seasons. (table 3.6A) 3.4.3A Relationship between grain yield, carbon isotope discrimination, canopy temperature depression and ash content under post anthesis water stress condition Under PAWS condition, grain yield showed significant positive correlation with biomass and HI in season. Significant negative correlation was observed ( ***, *** ) and ( ***, *** ) between canopy temperature depression 62

11 at boot stage (CTD b ) and canopy temperature depression at anthesis (CTD a ) in both the seasons respectively (table 3.5A). For ash content significant negative correlation ( *** ) was observed between grain yield and grain ash (m a G m ) in season. Grain yield also showed significant positive correlation (0.256 *** ) with leaf ash content at anthesis (m a L a ) in season. There is lack of correlation between GY, m a L a and m a G m in season. In season it showed significant positive correlation (0.337 ***, *** ) with plantlet leaf ash (m a L p ) and leaf ash content at boot stage (m a L b ) respectively. Grain yield showed significant correlation (0.447 *** and *** ) with leaf carbon isotope discrimination ( L a) and grain carbon isotope discrimination ( G m ) respectively in season. No correlation was found between GY, L a and G m.in season. Under limited irrigation condition, grain carbon isotope discrimination showed significant negative correlation ( ***, *** ) for canopy temperature depression at anthesis (CTD a ) and significant positive correlation (0.334 ***, *** ) for leaf carbon isotope discrimination ( L a ) in both the seasons (table 3.6A). Leaf carbon isotope discrimination at anthesis showed significant correlation (0.364 **, *, * ) for plantlet leaf ash (m a L p ), leaf ash at boot stage (m a L b ), and leaf ash at anthesis (m a L a ) only in seasons respectively. It showed significant correlation (0.291 * ) for leaf ash at maturity (m a L m ) only in season. It also showed significant negative correlation ( * ) for canopy temperature depression at anthesis (CTD a ) in season (table 3.6A) A Relationship between grain yield, carbon isotope discrimination, canopy temperature depression and ash content under well watered condition Under WW condition, Grain yield showed significant positive correlation with biomass and HI (0.492 ***, *** ) and (0.772 ***, *** ) in and season respectively. Negative correlation (-0.072, * ) and (-0.006,-0.238) was observed in both the seasons for canopy temperature depression at boot stage (CTD b ) and at anthesis (CTD a ) respectively. In season, CTD a showed significant negative correlation ( * ) with grain yield. For ash content, significant negative correlation ( **,-0,250 * ) was observed between grain yield and grain ash (m a G m ) in both the seasons. There is a lack of 63

12 correlation between GY, leaf ash at boot stage (m a L b ) and leaf ash at anthesis (m a L a ). In season GY showed significant positive correlation ( ** ) with plantlet leaf ash (m a L p ) which was not observed in season. Under WW condition GY showed significant positive correlation (0.447 *** and *** ) with leaf carbon isotope discrimination ( L a ) and grain carbon isotope discrimination ( G m in both the seasons (0.352 ***, ** ) and (0.528 ***, *** ) respectively. Grain carbon isotope discrimination showed significant positive correlation (0.450 *** ) for leaf ash at maturity (m a L m ). It also showed significant negative correlation ( ** ) for canopy temperature depression at anthesis (CTD a) in season and significant positive correlation (0.252 * ) in season. Significant positive correlation (0.387 ***, *** ) was observed between grain carbon isotope discrimination and leaf carbon isotope discrimination (table 3.6A) Leaf carbon isotope discrimination at anthesis showed significant correlation (0.310 * ) for leaf ash at maturity (m a L m ) and negative significant (0.379 **,-0.171) correlation observed for canopy temperature depression at anthesis (table 3.6A). 64

13 Table 3.6 A: Correlation between, m a and CTD a during and Year G m m a L p m a L b m a L a m a L m m a G m CTD a L a RSMS * 0.386** ** 0.386** *** *** PAWS *** 0.334** * ** *** WW *** * 0.252* 0.387** ** *** Year L a m a L p m a L b m a L a m a L m m a G m CTD a RSMS * *** ** ** 0.311* PAWS * ** 0.245* 0.282* * WW * * ** *, **, ***, significant at p=<0.05, 0.0 and respectively. ns = non significant RSMS: Residual Soil Moisture Stress, PAWS: Post Anthesis Water Stress, WW: Well Watered MaGm, m a L p, m a L b m a L a m a L m, magm: Ash content in grain at maturity, plantlet and flag leaf at boot stage, anthesis maturity and grain respectively; CTD a = Canopy temperature depression at anthesis L a and G m: Carbon isotope discrimination in flag leaf at anthesis and grain at maturity, respectively. 65

14 3.5A Discussion 3.5.1A Effect of water treatment on Grain yield, and m a Different irrigation treatments resulted in significant differences in grain yield, biomass, harvest index, carbon isotope discrimination and ash content.in all treatments, there was a strong decrease of discrimination,after anthesis.highest ash content values were obtained under WW environment followed by PAWS and RSMS environments at all stages except for plantlet leaf ash. Plantlet leaf ash showed highest ash content values under RSMS environment followed by WW and PAWS environment suggesting transpiration rate is higher in this treatment. Yield and biomass showed highest values under WW condition indicating high yield was associated with low transpiration efficiency. Similar results were obtained for previous season (Misra et al., 2006) A Relationship between GY,, CTD and m a under residual soil moisture stress Under RSMS condition, grain yield showed significant positive correlation with leaf carbon isotope discrimination ( L a ) and grain carbon isotope discrimination ( G m ). Monneveux et al.,(2005) reported a significant association between grain carbon isotope discrimination ( Gm) and grain yield under moderate residual soil moisture stress. The sign and the magnitude of the association between (whatever the stage and organ sampled) and yield under residual moisture stress seems to be depend highly on the quantity of water stored in soil at sowing as suggested by Monneveux et al.,(2005). According to Condon and Richards genotype with high discrimination values at vegetative stages tend to grow faster than low discrimination genotypes, under RSMS condition by covering the ground more quickly, they would be more efficient in reducing soil evaporation. The negative correlation obtained under RSMS treatment between grain yield and grain ash (m a G m ) has been previously reported in Barley (Febrero et al.,1994,voltas et al., 1998),durum wheat (Araus et al.,1998, Merah et al.,1999,2001a) and bread wheat (Tokatlidis et al.,2004) under severe terminal stress. On the other hand no correlation was found between yield and grain ash (m a G m ) by Monneveux et al., 2005 for wheat under RSMS condition. Non significant negative correlation was observed between grain yield and canopy temperature depression at anthesis (CTD a ). According to Reynolds et al., (1994), CTD 66

15 shows a good association with grain yield. Under RSMS condition, negative correlation was observed between yield and grain ash (m a G m ) and significant positive correlation with leaf carbon isotope discrimination ( L a ) and grain carbon isotope discrimination ( G m ) in seasons, suggests that mineral accumulation in kernels is probably regulated by physiological process other than transpiration and would be more related to re-mobilization A Relationship between GY, Δ, CTD and ma under post anthesis water stress (PAWS) condition In and season grain yield showed highly significant correlation with biomass and HI indicating the importance of biomass production and translocation of assimilates in determining grain yield. In season grain yield showed significant negative correlation with DF and DM indicating earliness is required in this environment. In both the seasons GY showed significant positive correlation with height suggesting that medium height is advantageous for higher yield. GY showed significant negative correlation with canopy temperature depression at anthesis (CTD a ).Canopy temperature depends on quantity of water transpired by the leaves. It is an integrative measure of a group of a mechanisms that ranges from radical absorption of water to the stomatal control of transpiration, when stomata close because of reduced water status, leaf temperature rises above ambient air temperature(ludlow and Muchow 1990).In fact under drought stress those genotypes present smaller canopy temperature will use more of available water in soil, thus limiting the negative effect of water stress on grain yield (Blum 1988). In season significant negative correlation was observed between grain yield and grain ash (m a G m ) which are in agreement with the results of Araus et al., (1998) and Merah et al., (1999, 2001) These results also fully confirm the results obtained by Voltas et al., (1992), Merah et al., (1999a) suggesting that the grain ash could be used as alternative criteria for grain carbon isotope discrimination ( G m ) to predict grain yield and in a range of climatic conditions, including under drought. On the other hand, in season there is no significant correlation between grain yield and grain ash but GY showed significant correlation with plantlet leaf ash (m a L p ) and leaf ash at boot stage (m a L b ). 67

16 In both the season GY showed significant correlation with L a and G m.according to Condon and Richards (1993), high discrimination genotypes tend to grow faster than low discrimination genotypes. By covering ground more quickly they are more successful in reducing soil evaporation having higher biomass at anthesis and more reserves they are able to translocate larger amount of stored assimilate to fill the grain. High may also reflect high stomatal conductance, particularly after anthesis when soil moisture decreases and stress becomes stronger. Ash concentration in mature grain could indicate the importance of retranslocation process during grain filling since discrimination ( ) and ash content in grain were negatively correlated in durum wheat (Merah et al.,1999).these result suggest that grain ash content is higher ( G being thus lower ) in genotypes more affected by drought during grain filling. According to Loss and Siddique (1994) photosynthesis is more affected by drought than translocation A Relationship between GY,, CTD and ma under well watered (WW) conditions Information on relationship between ash content, carbon isotope discrimination (CID), canopy temperature depression (CTD) and grain yield under irrigated condition is limited. GY showed significant positive correlation between biomass and HI and significant negative correlation with canopy temperature depression at anthesis (CTD a ). GY showed significant negative correlation with grain ash in both the seasons suggesting that grain ash could be used as alternative criteria for grain carbon isotope discrimination ( G m ) to predict grain yield.gy also showed significant correlation with L a and G m in both the seasons.gy showed significant positive correlation with plantlet leaf ash (m a L p ) which indicate that transpiration at seedling stage strongly influence the biomass production. A significant positive association was recorded between leaf ash at maturity (m a L m ) and grain yield in season. Greater transpiration increases the amount of passively transported minerals in leaves (Masle et al., 1992).A more efficient translocation of carbon products from the vegetative parts to grain could have contributed to an increase of mineral concentration in leaves(araus et al., 2001). 68

17 WW r=-0.348** MaGm RSMS r = PAWS r =-0.398** Yield MaGm PAWS r =0.004 RSMS r = WW r=-0.282* Yield Fig3.1A: Relationship between grain yield and grain ash in and seasons. 69

18 PAWS r =0.256** 17.0 MaLa RSMS r =0.235** WW r= Yield (04-05) PAWS r =0.188 MaLa WW r= Fig 3.2 A: Relationship between grain yield and flag leaf ash at anthesis in and seasons. RSMS r =0.149 Yield

19 22 21 PAWS r = WW r= MaLb RSMS r = Yield WW r = MaLb PAWS r = 0.448*** 9 RSMS r = Yield Fig 3.3A: Relationship between grain yield and flag leaf ash at boot stage in and seasons. 71

20 20 MaLp RSMS r = PAWS r = Yield WW r= 0.321** RSMS r = PAWS r = MaLp WW r = Yield Fig 3.4 A: Relationship between grain yield and plantlet leaf ash in and seasons. 72

21 PAWS r = 0.268* 17.0 CID La WW r = 0.528*** RSMS r = Yield CID La PAWS r = 0.353** WW r = 0.446*** 17.5 RSMS r = 0.447*** Yield Fig 3.5A: Relationship between grain yield and flag leaf discrimination at anthesis in and seasons. 73

22 22 21 PAWS r = WW r = 0.351** CID Grain RSMS r = Yield WW r = 0.513*** 17.5 CID Grain PAWS r = 0.435*** RSMS r = 0.568*** Yield Fig 3.6 A: Relationship between grain yield and grain carbon isotope discrimination in and seasons. 74

23 PART B: AESTIVUM WHEAT 3.1 B: Selection of wheat varieties and procurement of seed Twenty semi dwarf aestivum wheat genotypes were selected from All India Co-ordinated wheat programme, CIMMYT advanced lines and varieties from ARIs breeding material are included in the trial (table 3.1B) Table3.1 B: List of aestivum wheat genotypes included in and trial Sr.No. Name of the Source Suitable for Variety 1 GW 361 Junagarh,Gujarat rainfed 2 CBW 30 DWR, Karnal rainfed 3 MACS 6236 ARI,Pune irrigated 4 HI 1547 IARI RRS,Indore irrigated 5 CG 5026 Chhattisgarh,Madhyapradesh irrigated 6 GW 363 Junagarh, Gujarat irrigated 7 NIAW 917 ARS Niphad irrigated 8 MACS 2496 ARI,Pune irrigated 9 HD 2189 IARI Delhi irrigated 10 MACS 6158 ARI,Pune irrigated 11 GW 344 Junagarh, Rajasthan irrigated 12 IND 61 IARI RRS,Indore irrigated 13 MP 4028 Madhyapradesh irrigated 14 HI 1531 IARI RRS,Indore rainfed 15 MACS 6222 ARI,Pune irrigated 16 HI 1418 IARI RRS,Indore irrigated 17 GW 322 Chhattisgarh,Madhyapradesh irrigated 18 MACS 6221 ARI,Pune irrigated 19 UAS 231 UAS Dharwad irrigated 20 HD 2781 IARI Delhi rainfed 75

24 3.2 B Experimental conditions Experimental conditions were same as described in section and except for aestivum trials were conducted only in two different water regimes viz. limited irrigation condition (PAWS) and well watered condition (WW). 3.3 B Measurements Data on agronomical and physiological traits were recorded as per given in chapter 2, section , and chapter 3. section B Statistical analysis Data were analyzed using Agrobase 99 software. Combined anova was done to estimate G x E interaction over the environments and compare the differences between the environments. For, data from pooled sample were analyzed and SD was calculated. Phenotypic correlations (r) were estimated to determine the relationship between the traits and grain yield. 3.5 B Results Significant differences were found for grain yield between the two treatments in both the seasons i.e and seasons. The highest yields were recorded under WW regime followed by PAWS. Average yield for PAWS and WW was 4.26 and 5.62 t/ha in and 3.64 and 4.72 t/ha in season respectively. 76

25 Table3.2 B: Mean squares of combined ANOVA for GY, BIOM, HI, Ash content and CID under Limited Irrigation (PAWS) condition. Sourc sea son e of variat d.f Yield (T) Bioma ss(t) HI m a L p m a L b m a L a m a G m CTD a ion Treat ment *** 5 *** 72 *** 04 *** 4 *** 5 *** 5 *** 61 *** 200 Genot ype *** * ** *** ** * *** 6 *** *** * ** 4- Treat 05 ment Genot *** * ** *** ** * *** 1 *** *** * ** ype Treat ment *** *** *** 7 *** 45 *** 15 *** *** *** 200 Genot ype *** * ** *** ** * * ** *** *** * ** 5- Treat 06 ment Genot *** * ** *** ** * * ** * ** *** * ** ype 77

26 In both the seasons Genotype x Environment interaction was highly significant for yield, HI, plantlet leaf ash, and grain ash.highest grain ash values were found in PAWS followed by WW condition and for plantlet leaf ash the highest values were recorded under WW condition followed by PAWS condition. Exactly reverse trend was observed for durum wheat. Flowering duration ranged between and Maturity duration ranged between days. Highest biomass was obtained under WW condition followed by PAWS condition B Effect of water regime on grain yield, ash content and CID Water regime induced significant differences in ash content and grain yield.the highest plantlet leaf ash values were obtained under WW conditions suggesting that transpiration rate was much higher in this treatment. Similarly the highest grain ash values were obtained under limited irrigation condition followed by WW condition. Under PAWS and WW water regimes yield showed significant correlation for biomass and HI for both the seasons. Grain yield showed significant correlation with biomass and HI in both the seasons and for both the treatments. Whereas, under PAWS grain yield was negatively correlated with DF and DM in both the seasons. DF showed ( ***,-0.298) and DM showed ( ***, *** ) in and season respectively. Under WW condition, non significant negative correlations were observed for DF and DM in and season B Relationship between grain yield, canopy temperature depression (CTD) and ash content under PAWS condition Under PAWS, grain yield showed significant correlation with biomass (0.550 *, 0.374) and for HI (0.941 ***, ** ) in both the seasons. GY showed significant negative correlation with DF and DM in both the seasons suggesting that early maturity is required in this environment. There is lack of correlation for all ash content stages and canopy temperature depression at anthesis. There is significant positive correlation between grain yield and grain carbon isotope discrimination stage (0.473*, 0.454*) in nd season respectively. 78

27 Fig 3.1 B: Relationship between grain yield and plantlet leaf ash in and seasons. 79

28 Fig 3.2 B: Relationship between grain yield and leaf ash at anthesis in and seasons. 80

29 Fig 3.3 B: Relationship between grain yield and grain ash in and seasons. 81

30 Fig 3.4 B: Relationship between grain yield and canopy temperature depression at anthesis in and seasons. 82

31 Fig 3.5 B Relationship between grain yield and grain carbon isotope discrimination in and seasons. 83

32 Table 3.3 B: Ash content values, yield, biomass and harvest index under diff water regimes ( ) and ( ) Trait m a L p m a L a m a G m Yield(T/Ha) Biomass(T/Ha) HI CTD an CID_G season PAWS WW Mean Sd F value mean sd F value *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***

33 3.5.3 B Relationship between grain yield, CTD and m a under well watered condition Grain yield showed significant positive correlation with biomass (0.624 ***, *** ) and HI (0.680 ***, *** ) in and season respectively. Grain yield showed non- significant negative correlation for DF and DM in both the seasons. It also showed significant correlation for leaf ash at anthesis in both the seasons and non significant negative correlation for grain ash. There is lack of correlation between grain yield and grain carbon isotope discrimination. 3.6 B Discussion The highest grain ash and grain carbon isotope discrimination values were noted in the PAWS treatment which corresponded to severe water stress and resulted in lowest grain yield. Despite the strong terminal water stress grain carbon isotope discrimination values were higher in the PAWS treatment than those reported by Araus et al., (1997) and Merah et al., (2001c) probably because of higher water supply before anthesis and accelerated grain filling. The different irrigation treatments resulted in significant differences in grain yield, biomass, HI, carbon isotope discrimination and ash content. Ash content values in leaves at anthesis and at grain stage were higher than those reported. The mineral accumulation in kernels primarily depends on remobilization from leaves and stems and on minerals removed from the vegetative parts of the plant after the onset of senescence (Wardlaw 1990).Under drought stress, translocation is less affected than photosynthesis (Loss and Siddique 1994).Remobilization of minerals from vegetative tissues is consequently higher leading to increase in grain ash content (Masle et al., 1992, Merah et al., 1999).Thus, low leaf ash at anthesis and higher grain ash values observed in this study probably reflect severe terminal stress experienced by the crop and its effect on transpiration and remobilization. In this study, the highest values of leaf ash at anthesis were observed in WW conditions while the highest grain ash values were noted in the PAWS treatment. Similar results were obtained by Misra et al.,

34 Table 3.4 B: Correlation between phenological and morphological characters and yield in and season Treatment Year Biom HI DF DM PH m a L p m a L a m a G m CTD a CID_G PAWS * *** ** ** o.473* * ** * WW *** *** ** * *** **

35 3.6.1 B Relationship between grain yield, morphological and phenological traits Under water stress condition (PAWS), grain yield was significantly negatively associated with DF and DM in both the seasons.since wheat crop in the peninsular zone was generally exposed to heat and water stress, there is need to select for earliness under such conditions. Under both the water regimes, grain yield was highly significantly positively correlated to biomass and HI. HI showed a wide range of variation among the cultivars. Correlation between grain yield, biomass and HI under heat stress is well documented. Significant association was found in these conditions between grain yield and harvest index by Al-Khatib and Paulsen (1990), Rahman et al., (1997) and Singh et al., (1997). Reynolds et al., (1994) and Singh et al., (1997) also reported a positive association between grain yield and biomass under heat stress conditions. As a result, the average growth rate of biomass appeared to be a reliable and easy criterion for heat tolerance, regardless of the water availability B Relationship between grain yield, CTD, and m a under PAWS conditions The significant association between grain carbon isotope discrimination and grain yield observed under PAWS supports the results of Sayre et al., (1995), Araus et al., (1998), Merah et al., (2001b), Tsialtas et al., (2001), Monneveux et al., (2005), Misra et al., (2006) and Xu et al., (2007). Various hypotheses could explain this association. First, high grain discrimination could also characterize genotypes more dependent on the remobilization of pre-anthesis reserves for grain filling. Under severe post-anthesis water stress, photosynthesis is more reduced than translocation (Loss and Siddique 1994). Under these conditions, plants would mainly use assimilates from pre-anthesis reserves that were accumulated during period of reduced stress and have consequently higher values. This could also explain the positive correlation between and harvest index, observed in our experiment and by Merah et al., (2001c). Secondly, high grain discrimination could reflect an ability to maintain open stomata after anthesis, when soil moisture decreases and water stress becomes more severe (Morgan et al., 1993, Sayre et al., 1995, Merah et al., 1999, 2001b). 87

36 Finally, under conditions of high temperatures and high evaporative demand during grain filling (as was the case in peninsular zone), high discrimination, that reflects high leaf and canopy transpiration rates, may reduce leaf temperature and contribute to heat avoidance (Delgado et al., 1994, Sayre et al., 1995). However, leaf ash content, a trait associated with leaf transpiration (Masle et al., 1992), did not correlate to grain yield, in contrast to the results of Merah et al., (1999) and Tsialtas et al., (2002). The lack of relationship between and phenological traits, despite the large variation in phenology among cultivars, also disagrees with Araus et al., (1997) and Merah et al., (2001c). These differences are likely to be due to different environmental conditions and the germplasm used B Relationship between grain yield, canopy temperature depression, carbon isotope discrimination and ash content under WW conditions In the present study, grain carbon isotope discrimination was higher under WW than under water stress and was not associated with grain yield. These results were in full agreement with Monneveux et al., (2004b), Misra et al., (2006) and Xu et al., (2007).Information on the relationship between and grain yield under irrigated condition is limited. Grain yield of irrigated cereals was found to positively correlate with carbon isotope discrimination in the peduncle (Morgan et al., 1993) and grain (Araus et al., 1998, Fischer et al., 1998).In all these experiments, the crop experienced a subtle drought stress during the grain filling, despite the irrigation. However Condon and Richards (1993) observed a negative correlation between leaf discrimination and the biomass of young seedling cultivated in the absence of water stress. Under WW conditions, stomatal conductance is likely to be high in all cultivars resulting in increased Ci/Ca and discrimination values (Morgan et al., 1993), while increased photosynthetic capacity potentially decreases Ci/Ca. The decrease in Ci/Ca associated with increased photosynthetic capacity is consequently offset by the Ci/Ca increase resulting from stomatal aperture, hence reducing the possibility of association between discrimination and grain yield (Monneveux et al., 2005). A significant positive correlation was noted in this treatment between leaf ash at anthesis and grain yield. Ash content in leaf at anthesis consequently appears as a useful indirect selection criterion in this environment where does not show any correlation with yield. 88