The Effect of Terminal Heat Stress on Grain Growth and Quantitative and Qualitative Yield of Spring Bread Wheat in Ahwaz

Terminal heat stress in hot and dry conditions like Ahwaz reduces the quantitative and qualitative yield of wheat. In order to study the effect of terminal heat stress on grain filling period duration, grain filling rate and quantitative and qualitative yield of 20 spring bread wheat cultivars, a field experiment was conducted in Research Farm of Agricultural Sciences and Natural Resources University of Khuzestan, Iran in 2008-2009 as stripe block design and included four sowing dates (6 Nov., 6 Dec., 5 Jan. and 4 Feb.) in horizontal plots and 20 spring bread wheat cultivars in vertical plots with three replications. The analysis of variance showed that sowing date, genotypes and their interaction had a significant effect on measured traits. The mean comparison of interaction effect showed that in sowing date of 6 Dec. the highest grain yield (7254 kg/ha) was related to Chamran cultivar and the lowest grain yield (5445 kg/ha) belonged to Maroon cultivar. In terminal heat stress condition (sowing date of 4 Feb.), the highest grain yield (2323 kg/ha) was related to Maroon cultivar and the lowest grain yield (1258 kg/ha) belonged to Hamoon cultivar. Generally, in early (6 Nov.), timely (6 Dec.) and late (5 Jan) seeding, Chamran cultivar was suitable and in very late (4 Feb.) sowing, cultivars of Maroon, Virinak, Arvand and Atrak were suitable.