Identification of terminal heat tolerant bread wheat genotypes
Late sown irrigated wheat crop under Maharashtra condition always adversely affected by terminal heat during flowering and grain filling stage which results in reduced grain yield. A study was undertaken to identify terminal heat tolerant bread wheat genotypes on the basis of different stress indices. Material under study comprised of newly developed nineteen bread wheat genotypes and three recommended varieties as check. Two separate experiments were conducted at Niphad under timely and late sown conditions during rabi 2013-14. Yield trait was recorded and per cent yield reduction under late sown condition as compared to timely sown condition was estimated. On the basis of yield trait different stress susceptibility and tolerance indices were estimated. Among the new genotypes studied, NIAW 2972 had highest yield potential under both, timely (48.66 q/ha) and late sown condition (46.99 q/ha) with minimum yield reduction (3.43 %) under late sown condition except the check variety NIAW 34 (1.75 % yield reduction). On the basis of combined analysis of performance of wheat genotypes under both the sowing conditions, per cent yield reduction under late sown condition and estimates of different stress indices, variety NIAW 34 was found to be most terminal heat tolerant which was closely followed by the genotype NIAW 2972. NIAW 34 (SSI=0.17) possessed highest level of terminal heat tolerance followed by NIAW 2972 (SSI=0.34) and HI 977 (SSI=0.39). Correlation analysis indicated that yield under stress environment had significant (p<0.05) positive (r=0.95) association with that of non stress environment. Yield under both sowing condition had significant positive correlation with MP, GMP and HTI while negative significant correlation with SSI and TOL. First two factors of Principal component analysis explained 99% variation to which 93% and 6% was contributed by first and second factor respectively while maximum contribution to first component was from YLS followed by HTI, GMP and MP. The Genotype NIAW 2972 and two check varieties viz., NIAW 34 and HI 977 were identified as terminal heat tolerant and can be used directly as well as in the crossing programme for developing terminal heat tolerant variety or line.
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