ارزیابی ارقام گندم نان در شرایط نرمال و تنش رطوبتی آخر فصل از نظر صفات زراعی

     In order to study the effect of drought stress and determination of effective traits on grain yield of wheat in normal and terminal drought stress conditions, 82 wheat genotypes were studied in two separate experiments using randomized complete block design with three replications during cropping season 2011-2012. Drought stress was applied in heading stage by limited irrigation. Set of 22 traits including yield and yield components were measured. Results of analysis of variance showed that in both conditions there are significant different between all genotypes for all traits. Drought stress decreased all traits except number of leaves on the main stem and the number of tillers. The highest genetic diversity in two conditions were for awn length, grain yield and number of fertile tiller. Pearson simple correlation, stepwise regression analysis and path analysis in both conditions on all traits took over. In stress condition amount of correlation between grain yield with biological yield, straw yield, harvest index, Fertile spikes per square meter and total number of tillers per square meter equal to or greater than 50% was achieved. In both environments, the highest correlation was found between biological yield and grain yield. The results indicate the importance of peduncle length in becoming greater amount of grain yield under drought condition. Based on stepwise regression analysis in normal irrigation 6 variables and in stress conditions 5 variables entered the model and in total more than 80% of the changes were justified. To determine the direct and indirect effects of traits on yield, path coefficient analysis was done, the most direct effect on grain yield in both conditions belonged to biological yield. Based on this study the most important traits that are introduced as an indicator for selection high yielding varieties of wheat in both conditions, are biological yield, spike weight, number of fertile spike and 1000 kernel weight. Also the effective role of height plant in stress condition, selection of higher plants in addition to more spikes in increasing grain yield be important.