YIELD REDUCTION ANALYSIS OF BREAD WHEAT UNDER HEAT STRESS AT TWO DIFFERENT ENVIRONMENTS IN PAKISTAN

Terminal heat stress has become an alarming threat for bread wheat in warm humid zones. Heat susceptibility index (HSI) of 51 genotypes from diverse parentage was calculated for estimation of yield reduction for two consecutive years. In the field experiment, terminal heat stress was provided through late sowing during the years 2014 and 2015. Mean heat susceptibility index (HIS) was 1.02 and 0.97 for both the years. Overall 50% yield reduction was observed due to terminal heat stress. Treatment results were significant with 9. 928 mean square. On the basis of HSI of two years, the best tolerant nine genotypes were sorted out for the breeding purposes. This might be one of the effective strategies toward production of heat tolerant wheat germplasm. Heat sensitivity index parameter allowed the selection of best varieties and such germplasm can also be used for gene pyramiding for climate change resilience.