Heat tolerance in relation to acquired thermotolerance for membrane lipids in bread wheat

Cell membrane stability (CMS) and tetrazolium triphenyl chloride (TTC) test, heat susceptibility index (HSI), heat response index (HRI) and grain yield were used to evaluate diverse 28 bread wheat genotypes including parents and their progenies under normal and heat stress conditions for two years. The genotypes differed significantly for all the characters indicating considerable variation for improvement of these traits. The varieties WH 1021 had a desirable combination of grain yield and heat tolerance potential, while WH 730 had a combination of cellular thermotolerance (TTC and chlorophyll fluorescence), heat tolerance (HRI) and high grain yield under heat stress conditions. Correlation coefficients revealed that HRI was the most important trait followed by TTC because the genotype having high HRI also had high grain yield and showed better mitochondrial viability and membrane stability under heat stress. The use of the parents with high GCA effects, namely, NIAW 34 and WH 730 and WH 1021 in crossing programme for thermotolerance may provide desirable segregants for improvement of heat tolerance in material under study.