Path Analysis of Yield Related Traits in Wheat Genotypes under Normal Irrigation and Drought Stress Conditions

For identification of correlations and relations among different traits in bread wheat, 30 genotypes were investigated based on a split plot experiment in the form of randomized complete block design with three replications under normal and moisture stress conditions during the 2016-2017 crop season. The results of the analysis of variance showed that the effect of genotypes was significant for most of the studied traits. The interaction effect of drought stress and genotype was significant for all examined traits except 1000-grain weight. Genotypes c-94-3 and Heidari were recognized as the best genotypes with average grain yield of 437 and 427 g/m2, respectively, in normal conditions. Under drought conditions, genotypes cd-4 and cd-6 had the lowest grain yield with an average of 104 and 108 g/m2, respectively. Based on the results of multiple regression in field experiment, under optimal irrigation conditions, flag leaf area, spike density,  number of days to 50% flowering and spike length, (R2= 0.466) and under stress conditions, grain filling rate, grain filling period and straw yield (R2= 0.736) were considered as important traits affecting grain yield.  Path analysis of grain yield under normal conditions indicated that the flag leaf area, spike density and spike length, and under stress conditions, the grain filling rate, grain filling period and straw yield, with the greatest direct positive effect were the important and effective traits in grain yield. Based on the results of the analysis of the grain yield correlation coefficients under normal condition, the number of kernels per spike, 1000-grain weight, flag leaf area, spike density and spike length, and under stress conditions, the number of kernels per spike, the grain filling rate, grain filling period and straw yield, were considered as the traits affecting grain yield.