Genetic Analysis between Traits Associated With Grain Yield in Wheat Genotypes under Full Irrigation and Grain Filling Stage Stress Conditions.

To evaluate the genetic diversity and identify relationships among traits in 20 wheat genotypes, two experiments were conducted based on randomized complete blocks design with three replications, in two separate conditions of full irrigation and late drought stress, in two locations of Miyandoab and Hamedan during 2006-2007. Means comparison showed under full irrigation condition, genotype 2 with 8.980 t/ha, genotypes 2 and 13 under late drought stress condition with 6.800 and 6.900 t/ha, respectively had the greatest grain yield. Correlation coefficients between traits showed that grain yield had positive significant correlation with plant height (0.24**) and biomass (0.59**) in full irrigation, and with biomass (0.83**), awn length (0.49**), number of seed /spike (0.41**) and harvest index (0.25**) in grain filling stage stress condition. Grain yield showed negative significant correlation with days to maturity, too. Stepwise regression analysis showed under full irrigation condition, biomass and harvest index (R2 = 0.97) and in late drought stress condition biomass, harvest index and number of grains per spike (R2 = 0.97) had major effect on grain yield and entered to final model. Path analysis indicated that biomass had highest positive direct effect on grain yield whereas it had negative effect through harvest index on grain yield (in both conditions). In two environmental conditions, selection based on grain yield could be effective, biomass and harvest index were identified as traits that are important in grain yield variations and genotype 2 identified as the best genotypes for two conditions.