Munjal, RenuSeema2016-09-062016-09-062013http://krishikosh.egranth.ac.in/handle/1/75491The objectives of present investigation were to determine the variation for morphophysiological traits, to identify physiological traits related to heat tolerance and to identify physiological traits using SSR markers grown under normal and terminal heat stress late sownconditions. The characters observed were grain yield/sq. meter (g), number of productive tillers/meter row length, 100-grain weight (g), grain weight/spike (g), number of spikelets/spike, days to heading, days to maturity, plant height at 45 days (cm), plant height at maturity (cm), biomass/sq. meter (g). Data on four physiological traits viz., canopy temperature depression, membrane thermostability, chlorophyll fluorescence and 2,3,5-triphenyl tetrazolium chloride were also recorded. Results revealed that the mean of genotypes in two environments (normal and late sown) were significant for the characters viz., grain yield/sq. meter (g), number of productive tillers/meter row length, number of spikelets/spike, days to heading, days to maturity, plant height at maturity (cm), biomass/sq. meter (g). This indicated that genotypes of bread wheat differed in their response to terminal heat stress for these characters. The genotype WH730 showed least inactive reaction centres in late sown conditions indicating the high efficiency in photosystem- II. The magnitude of direct effects showed that grain weight/ spike and spikelets/ spike were important for improvement of grain yield in normal sown conditions. The direct contribution of cell membrane stability followed by plant height at 45 days were important for improvement of grain yield in late sown environment. The NTSYS-PC UPGMA cluster tree analysis led to the grouping of 21 wheat genotypes in two major groups and 7 subgroups. Cluster V was the largest consisting of 6 genotypes (DBW17, MP4010, RAJ3765, HD2687, HD2931 and HD2967) followed by cluster IV consisting of 5 genotypes (WH730, WH1100, WH1111, WH1021 and DBW14), cluster III and VI consisting of 3 genotypes-WH416, WH542, WH711 and PBW343,SONALIKA and PBW550 and cluster II (2 genotypes-DBW16 and PBW590) and cluster I and cluster VII (1 genotype each-WH147 and PBW373) . WH1100 and WH730 showed a maximum similarity coefficient of 0.86. The molecular size difference between smallest and largest allele at a locus varied from 30 to 450 bp.enTerminal heat stress, bread wheat genotypes, physiological traits, genetic diversity.Thesis