Grain growth rate and heat susceptibility index: Traits for breeding genotypes tolerant to terminal high temperature stress in bread wheat (Triticum aestivum L)

High temperature stress has an adverse effect on wheat productivity. To generate information on the effect of high temperature on various morpho-physiological yield attributes, which would help in developing high temperature stress tolerant genotypes, an experiment was conducted on a set of 15 diverse cultivars, recommended for different sowing conditions. The experiment was planted on three sowing dates to subject the material to different temperature regimes in the cropping period. The results revealed that early maturing genotypes like HD2285, HD2307, Sonalika UP2338, Lok1 and C306, showed better performance under high temperature stress conditions with less reduction in grain yield and have relatively higher grain growth rates with more tolerance to heat stress for most of the yield attributing characters (low HSI values). The characters GGR and HSI could be taken as Important criteria for breeding genotypes acclimatised to late planting conditions.