Evaluation of drought tolerance in promising lines and cultivars of bread wheat (Triticum aestivum L.)

To identify genetic differences among bread wheat genotypes for drought tolerance, 30 genotypes of bread wheat were evaluated in two separate and simultaneous experiments in a randomized complete block design with three replications both under non-stress and late season drought stress conditions during cropping seasons of 2009-2010 at the Agricultural Research Station of Islamic Azad University, Tabriz Branch, Iran. Combined analysis of variance indicated that there was a highly significant diversity (p <= 0.01) among the genotypes for grain yield. Interaction of genotype x stress condition was also significant. Mean comparisons showed that Alvand and C-86-produced highest grain yield in non-stress and stress conditions, respectively. Stress tolerance index (STI), geometric mean productivity index (GMP) and harmonic mean index (HARM) showed highly significant correlations with grain yield under both stress and non-stress conditions. They are thus assumed to be appropriate indices for the selection of tolerant genotypes. By using a three-dimensional plot and cluster analyses based on these indices, Mandavi, C-84-8 and Navid cultivars were identified as superior genotypes. Based on principle component analysis, the first two components explained 99% of variations; the first and second components were named as tolerance and sensitivity components, respectively.