Effects of terminal drought on grain yield and some morphological traits in wheat (Triticum aestivum L.) genotypes

This study was conducted to evaluate grain yield and some of morphological traits in 20 promising wheat genotypes under non-stressed and post-anthesis drought stress conditions at Arak Agricultural Research Station during 2001/02 and 2002/03 cropping seasons. Experimental design was randomized complete block with three replications. Peduncle weight, grain number per spike, grain weight per spike, 1000 kernel weight, harvest index and grain yield were measured from plant samples taken at anthesis and maturity. Results of combined analysis of variance showed significant difference among genotypes for most of the measured traits. Under stress conditions grain weight per spike showed positive and highly significant correlation with harvest index (r=0.87**) and grain number per spike (r=0.76**). Days to heading showed positive and significant correlation with peduncle weight at anthesis. Harvest index also showed positive and highly significant correlation with grain number per spike (r=0.55**) and 1000 kernel weight (r=0.82**). Under non-stress conditions, grain weight per spike showed positive and highly significant correlation with harvest index (r=0.79**). Grain yield ha-1 also had positive and significant correlation with harvest index (r=0.67**), grain weight per spike (r=0.50*) and 1000 kernel weight (r=0.56*). Based on positive and highly significant correlation of grain yield with MP, GMP and STI under both non-stress and stressed conditions, these indices were identified as reliable criteria to select genotypes under terminal drought stress condition. Based on path analysis, direct effect of harvest index on grain yield was positive (0.76). The most indirect and positive effect of harvest index on grain yield was via grain number per spike and 1000 kernel weight. The most positive and negative direct effects on grain yield belonged to 1000 kernel weight (1.11) and grain weight per spike (-1.05), respectively.