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Heat stress is increasing drastically and has become a major threat to wheat production in various wheat growing regions. Exposure of wheat genotypes to temperatures above the critical threshold level during flowering and grain-filling stages can cause reproductive failure and grain yield reduction. To withhold this situation, a research was carried out on twenty bread wheat genotypes viz. AS-11, AS-12, AS-13, AS-14, AS-15, AS-16, AS-17, AS-18, AS-19, AS-20, AS-21, AS-22, AS-23, AS-24, AS-25, AS-26, AS-27, AS-28, AS-29 and Chakwal-86 (check), at the Experimental Field, Nuclear Institute of Agriculture (NIA), Tandojam. The experiment was conducted in Randomized Complete Block Design having three replications during Rabi season, for evaluating the response of terminal heat stress in wheat genotypes. The analysis of variance revealed significant differences among the genotypes at both normal and high temperatures. Reduction in various traits was observed due to late planting, which indicated visible effects of high temperature on physio-yield traits. On the basis of average performance, tillers plant-1, spikelets spike-1, grain yield plant-1, grains spike-1, grain weight of main spike-1 and biological weight plant-1 showed reduction of 24.83, 7.1, 39.78, 14.87, 25.49 and 37.41, respectively under heat stress conditions. However, minimum reduction under heat stress was manifested in the wheat genotypes as AS-15, AS-26 and AS-13 for various traits, suggesting their presence of heat tolerance. Nonetheless, the advance lines AS-14 and AS-19 expressed maximum decline under heat stress displaying their susceptibility to heat stress conditions. The remaining genotypes exhibited moderate heat stress tolerance. Thus, the selected advance lines have great potential for heat tolerance and can be utilized for future breeding program.
Keywords: Bread wheat; Heat stress; Morpho-yield traits; Temperature