the effects of terminal heat stress on yield, yield components and some morpho-phenological traits of barley genotypes (hordeum vulgare l.) in ahvaz weather conditions

terminal heat stress is the most widespread heat stress in the world. in order to evaluate the effect of heat stress on yield, yield component, and mopho-phenological traits of barley, 10 barley genotypes including the 2-row genotypes: mahour, khoram, nimrooz, abidar and 6-row genotypes: yousef, rihan 03, izeh, zahak, nosrat, jonoub were tested under normal (optimum sowing date) and heat stress (late sowing date) conditions in experimental field of shahid chamran university of ahvaz. the experiment in each condition was arranged in a randomized complete block design. terminal heat stress caused significant reduction in days from sowing to heading (38%), days from sowing to maturity (34%), plant height (47%), peduncle length (36%), biological yield (52%),  spike length without awn (21%), number of spikelet per spike (31%), number of kernels per spike (36%), 1000 kernel weight (7%), harvest index (7%) and grain yield (42%). according to the results, in normal condition yousef with 5.4 t/ha and in stress condition rihan 03 and jonoub with 3.4 t/ha have the maximum grain yield. abider in both conditions showed the minimum yield. based on the results, the maximum correlation coefficient was observed between harvest index and grain yield in both conditions, heat stress (r=0.77, p ≤0.01) and normal (r=0.91, p ≤0.01), suggesting the considerable role of this trait for evaluating the barley genotypes in heat stress experiments. 6-row barley genotype had superiority for most of traits in compare to 2-row genotypes and finally gave more grain yield in both conditions.