Yield Attributes and Qualitative Characters of Durum Wheat as Affected by Terminal Drought Stress

Water stress has adverse effects on crop yield and food quality. In this study, a diverse set of durum wheat genotypes including Iranian landraces and some new cultivars; ICARDA and SIMMYT accessions; and a few foreign landraces were evaluated for agronomic and biochemical traits. Two field experiments were conducted in randomized complete block designs with three replicates under supplementary irrigated (non-stress) and rain-fed (terminal drought stress) environments using the 73 durum wheat genotypes. A combined analysis of variance indicated highly significant genotypic differences for all the traits. Terminal drought stress decreased grain yield, 1000-grain weight and the number of grains per spike, while total gluten content and grain protein content increased. In both experiments, grain yield was positively correlated with the number of spikes per m 2 and the number of grains per spike. Gluten index showed a significant negative correlation with wet, total and dry gluten. Grain protein content was positively correlated with wet, total and dry gluten in the both conditions. In order to identify terminal drought-resistant genotypes, drought tolerance indices including tolerance index (TOL), stress tolerance index (STI), mean productivity (MP), geometric mean productivity (GMP), stress susceptibility index (SSI), and yield stability index (YSI) were calculated. Among the indices, GMP, MP and STI were positively correlated with grain yield in both environments. The results of this study showed that yield and yield components were affected by environmental factors, while qualitative characters were more affected by the genotype (genotype dependent). Some superior durum wheat accessions were identified and may be used in breeding programs, as well as for food and industrial products. The application of principal component analysis (PCA) to discriminate the durum wheat genotypes has been discussed.