The Response of Iranian Spring Wheat Cultivars to Heat Stress at Anthesis and Grain Filling Stages

Heat stress is one of the most important limitations of agricultural production across the world. High temperature significantly influences water status, biosynthetic pathway, morphology, phenology, yield and quality of wheat. In order to study the effects of heat stress on yield and yield components of wheat, 33 spring cultivars were evaluated in two randomized complete block designs with three replications in Ahvaz (hot) and Karaj (moderate climate). Heat stress applied through late sowing, so that the plants encountered to temperatures exceeding 30°c at terminal growth stages. Days to flowering, days to maturity, peduncle length, plant height, spikes per square meter, seed per spike, thousand kernel weight and yield were measured. Analysis of variance and mean comparison indicated that cultivars were significantly different in most of the traits measured. At Ahvaz, Chamran, Kauz and Dez were the most tolerant while Hamoon, Montana and Kavir were the most susceptible cultivars. Kauz, Behrang and Darya were the most tolerant and Babax, Montana and Neyshaboor, the most susceptible ones in Karaj. The number of spikes per square meter and thousand kernel weight were affected the most by heat at Ahvaz. However, at Karaj spikes per square meter and kernels per spike were profoundly impacted by heat stress. Correlation and regression analyses demonstrated that days to maturity and kernels per spike were the most critical, traits for screening under stress in Ahvaz and Karaj conditions, respectively.