EFFECT OF HEAT STRESS ON SOME AGRONOMIC TRAITS OF BREAD WHEAT (TRITICUM AESTIVUM, L) GENOTYPES UNDER UPPER EGYPT CONDITIONS

Abstract

Combined analysis of variance for all studied traits in twelve breadwheat genotypes showed highly significant differences among lines andsowing dates, as well as, the lines x sowing date interaction whichshowed significant and highly significant for all traits except grain yield.Delaying the sowing date to 20 December reduced grain yield, 1000kernel weight, accumulated growing degree days (GDD), and duration ofgrain filling period by 30.0, 6.2, 10.3, and 11.4%, respectively whencompared to normal sowing date (20 December), while the rate of grainfilling period was increased by 7% when compared to the optimumsowing date (25 November).Susceptibility index “s” for grain yield showed that lines 1, 2, 3, 7, 9and 10 were the most tolerant lines to high temperature, meanwhile theother lines were the more susceptible. Line number 5 recorded thehighest grain yield, longest duration with medium rate of grain fillingunder late sowing date. These results indicated that the tolerant lines mayhave genes controlling tolerance to heat stress. Hence, they could be useas parents in breeding programs in Upper Egypt.