Genotypic Variation for Physiological Traits Associated with Heat Tolerance in Bread Wheat (Triticum Aestivum L.)

Twenty five genetically diverse bread wheat varieties were evaluated in two environments viz., non-stress (mid November sown, &,) and heat stress (mid December sown, E2), for grain yield and physiological traits related to heat tolerance. Significant differences among environments indicated sensitivity of grain yield and related physiological traits to heat stress. Highest yielding genotypes were Raj 4014, CBW12, HW 2044 and Raj 4027 in non stress and HUW 543, Raj 4014, Raj 4012 and Raj 4027 in heat stress enviornments. Under heat stress conditions, HUW 543 was a desirable genotype for grain filling period, 1000-grain weight and chlorophyll loss, whereas Raj 4014 had desirable combination of 1000-grain weight and memberane injury. Genotypes Lok 1, Raj 4024 and Raj 4012 showed least heat susceptibility index for grain yield. A reduction of 28.9 per cent in grain yield in response to heat stress was observed. Heat stress caused a reduction of 39.7, 19.4, 8.5, 7.6 and 5.6 per cent for canopy temperature depression (grain filling stage), chlorophyll loss, 1000-grain weight, grain filling period and memberane injury (grain filling stage), respectively.