Evaluation of Drought Tolerant in Some Wheat Genotypes to Post-anthesis Drought Stress

Water deficit is the major cause of wheat (Triticum aestivum L.) yield losses in Iran and many other regions where the crop is not normally irrigated. The aim of the present study was to evaluate the ability of several selection indices to identify drought-resistant wheat genotypes. Twenty-one bread wheat genotypes were evaluated under two field experiments (post-anthesis drought stress and normal conditions). The experiments were arranged in a randomized complete block design with three replications in two successive growing seasons (2007/2008 and 2008/2009). The results showed that yields in the normal conditions were positively correlated with yields in the stress conditions. Several genotypes with good performance under both conditions were identified. Correlation analysis indicated that the most suitable drought tolerance criteria for screening substitution genotypes were mean productivity (MP), geometric mean productivity (GMP) and stress tolerance index (STI) (Group A genotypes) and when the stress was severe, stress susceptibility index (SSI) was found to be more useful index in discriminating resistant genotypes. Based on different drought indices, genotypes G4, G14 and G9 had the best ranking. In addition bi-plot and cluster analysis cleared superiority of these three genotypes in both seasons.