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Leaf membrane stability (LMS) and the tetrazolium triphenyl chloride (TTC) test, heat susceptibility index (HSI), heat response index (HRI) and grain yield were used to evaluate 20 diverse wheat genotypes under normal and heat stress conditions for 2 years. The varieties ÔSeriÕ and ÔRaj 3765Õ had a desirable combination of cellular thermotolerance (TTC and LMS), heat tolerance (HRI) and high grain yield potential under heat stress, while ÔWH 730Õ and ÔWH 533Õ were better in cellular thermotolerance and heat tolerance. The varieties ÔPBW 373Õ and ÔKauzÕ also performed better under heat stress in terms of grain yield and HSI/ HRI. The varieties ÔKanchanÕ, ÔPBW 373Õ, ÔNIAW 34Õ and ÔGW 173Õ were avoiders/escapers, ÔSeriÕ and ÔHUW 234Õ were tolerant to heat stress, while ÔWH 730Õ, ÔWH 533Õ, ÔNesserÕ, ÔRaj 3765Õ and ÔKauzÕ showed a combination of both. 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 was better in mitochondrial viability and membrane stability under heat stress. Significance of GCA and SCA variances indicated the presence of both additive and dominant types of gene action. The use of the parents with high GCA effects, namely, ÔRaj 3765Õ and ÔWH 730Õ in a crossing programme for thermotolerance may provide desirable segregants through selection.

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