the effects of terminal heat stress on yield, yield components and some morpho-phenological traits of wheat genotypes in ahwaz weather conditions

heat stress is one of the main obstacles for crop production in many areas of the world including southwest of iran. in order to evaluation the effect of heat stress on yield, yield component, and mopho-phenological traits of wheat, an experiment was conducted during 2010-2011 under normal (optimum sowing date) and heat stress (late sowing date) conditions on 11 wheat genotypes including yavaroos, zagros, chamran, niknejad, koohdasht, alvand, montana, m6, kauz, gohar and durum-ch-89 in experimental field of shahid chamran university of ahwaz. the experiment in each condition was arranged in a randomized complete block design. terminal heat stress caused to significant reduction in days from sowing to heading (29%), days from sowing to maturity (35%), plant height (31%), peduncle length (27%), head length with awn (12%), head length without awn (15%), number of spikelet per spike (15%), number of kernels per spike (19%), 1000 kernel weight (14%), biological yield (37%) and harvest index (5%), and spike/m2 so that these effects resulted in a significant reduction in grain yield (41%). based on the results morpho-phenological traits were detected as important traits in heat stress studies but number of kernels per spike and harvest index were recommended as convenient traits for screening the heat tolerant lines. kauz, chamran and alvand cultivars were able to maintain the grain yield under heat stress condition and suggested as tolerant cultivars. these cultivars have potectial for direct planting in warm areas or using in breeding programs.