Evaluation of bread wheat populations for drought stress

In order to study changes of agronomic traits under drought stress and identification of tolerant germplasm, a total of 484 accessions of bread wheat collection of National Plant Gene Bank were studied in Yazd field under normal and drought stress conditions by planting tolerant cultivars (Kavir, Roshan and Mahooti). Drought stress was applied by irrigation stoppage after cultivation. Evaluation of agronomic traits was carried out in accordance with international descriptor both for 71 drought survived accessions and the same accessions under normal condition. Analysis of descriptive statistics showed that the grain weight of five spikes under normal condition and the number of fertile tillers under drought stress had the highest coefficient of variation. The highest mean reduction in traits under drought stress was observed for grain weight of five spikes (23.8%) and then for the number of fertile tillers (21.1%). In almost all traits evaluated, some accessions were superior to control cultivars in both normal and drought conditions. Grain weight of five spikes under drought stress was significantly correlated with florets number per spikelet (r = 0.272*), grain number per spike (r = 0.742**), one-hundred-grain weight (r = 0.663**), grain filling period (r = 0.314**) and days to spike emergence (r = -0.238*). The accessions were divided into four groups under drought stress and normal conditions using cluster analysis dendrogram. Distinction among clusters was confirmed by discriminant analysis. The superior accessions identified in this study can be used in drought tolerance wheat breeding programs.