Heat stress is one of the major wheat (Triticum aestivum) production constraints in South Asia (SA), particularly in the Eastern Gangetic Plains (EGP) of India and Bangladesh. Malnutrition is also a severe problem among children and women in SA. Wheat varieties with high grain Zn/Fe are a sustainable, cost-effective solution in the fight against hidden hunger. Thirty wheat genotypes were characterised under the optimum temperature and heat stress conditions in 2016–2017 and 2017–2018 to study the response of the stress on the yield, physiological traits and grain Zn/Fe content. A significant genetic variation was observed for all the traits under the optimum temperature and stress conditions. The yield was reduced by an average of 59.5% under heat stress compared to that of the optimum temperature. A strong positive association of the canopy temperature depression (CTD) with the grain yield (GY) was observed under the heat stress. A negative correlation of the grain Zn/Fe with the yield was observed under the optimum temperature and heat stress conditions, while the association between the grain Zn and Fe was positive. The genotypes BRW 3723, BRW 3759, BRW 3797, BRW 160, HD 2967, HD 2640 were found to be heat-tolerant in both years. Among the tolerant genotypes, BRW 934, BRW 3807 and BRW 3804 showed a high zinc content and BRW 934, BRW 3797, BRW 3788 and BRW 3807 showed a high iron content, respectively. These genotypes can be explored in future breeding programmes to address the problem of nutritional deficiency.

Terminal heat stress is one of the major production constraints in wheat-producing areas of south-east Asia. The selection of genotypes based on grain yield per se is not effective under stress condition. In the present study 30 wheat (Triticum aestivum L.) genotypes were evaluated under normal and heat stress conditions during 2016-17 and 2017-18 to determine the suitable trait index for selection of genotypes under non-stress and heat stress environments and identification of heat tolerant genotypes. The observation was recorded for 13 morphological, biochemical and physiological traits. The index based on seven characters like grain yield, days to heading, biological yield, green fodder yield, dry matter content, catalase and peroxidase was most suitable with the genetic gain of 4856.09% and the genetic advancement of 33.09 in normal condition and the index based on five characters comprising days to heading, biological yield, number of tillers, catalase and peroxidase was most suitable with an expected genetic gain of 20101.32% and genetic advance of 35.09. The genotypes RAJ 3765, BRW 3794, HD 2643, SW 129, DBW 14, SW 160, BRW 3759, BRW 3762 and BRW 3800 were identified as moderately tolerant considering selection index score and heat susceptibility index. These genotypes may be promoted for cultivation under late sown conditions and used as parents for the development of genotypes tolerant to terminal heat stress.