The Response of Different Bread Wheat Genotypes (Triticum aestivum L.) to Temperature Changes

Increased temperature is a major yield declining factor in wheat production. Current study was intended to evaluate the impact of increased temperature on the pre and post reproductive major yield attributing biometrical traits through the use of stress tolerance indices and trait reduction ratio (%) of all the traits studied. A set of 27 genotypes including 2 check entries viz., Shriram 303 and HD 2967 was evaluated in two separate trials, timely sown (non-stress) and late sown (heat stress) conditions in RBD design with three replications during rabi 2020-21 at the agriculture research farm of Rama university, Kanpur. Significant dropping in major yield attributing traits have Such as grain yield/plant, grain yield/spike and tillers/plant exhibited 54.41%, 39.31 % and 34.22% reduction, respectively thought the estimation of trait reduction ration (%) specially for the trials conducted under the late sown (heat stress) condition as compared to the normal sown trial. Five stress tolerance indices viz., susceptibility index (HSI), mean productivity (MP), tolerance (TOL), heat tolerance index (STI) and trait stability index (TSI) have been estimated to find out the heat stress tolerance and susceptible genotypes for grain yield under high temperature stress conditions. Correlation estimates of different heat stress tolerance indices with grain yield in non-stress condition (timely sown) exhibited significant positive association with MP (0.766**), HTI (0.622**), TSI (0.414*), and TOL (0.284). Though, under heat stress condition (late sown), grain yield displayed a significant positive correlation with HTI (0.713**), MP (0.707**), TOL (0.517**), TSI (0.656**) and negative correlation with HSI (-0.608**). Through the correlation analysis estimates, four heat stress indices viz. HSI (heat susceptibility index), MP (mean productivity), STI (stress tolerance index) and TSI (trait stability index) have been used in assorting the heat tolerant wheat genotypes. Current estimates directed that 14 genotypes (PBW 152, HUW-206, WL-2, WL-8, WL-13, DBW-71, DBW-39, WH-1105, HUW-318, PBW-154, ALWL-5, WL-14, PBW-502 and Shriram 303) were heat tolerant genotypes while 8 genotypes (Jamuni, F 2004, Allahabad Local, Black, U. P Local, YOUDA, U. P B2425 and HD 2967) have been observed high temperature susceptible. While WH-1105 and PBW-154 have been observed high yielding genotypes under heat stress environment. Therefore, genotypes WH-1105 and PBW-154 were acknowledged as a suitable genotype for late sown trial. Further, these two genotypes could be utilize in breeding programme to develope heat tolerant varieties of wheat.