The influence of late-season drought stress on grain yield, its components and some other morpho-physiological traits was evaluated using 151 F3 families obtained from crossing a drought tolerant genotype with a drought susceptible genotype at Research Farm of Isfahan University of Technology in 2003-2004. Two separate randomized complete block designs each of which having two replications allocated to each of moisture stress and irrigated (non-stress) environments. Drought stress significantly affected grain yield, its components, harvest index and relative water content (RWC) traits. Analysis of variance of combined data revealed significant differences among the environments for the traits that related to reproductive stage. The genetic and phenotypic correlation coefficients between grain yield and most of traits such as RWC and excised leaf water retention (ELWR) were significant. Based on stepwise regression analysis, biological yield and harvest index were the most efficient traits in explaining the grain yield variation under normal and stress environments, respectively, Factor analysis of data from the two environments indicated that components were related to phenologic characters, potentional of plant production, harvest index and yield components, plant height and physiological traits. The amount of variation explained by these components varied for two environmental conditions where yield components, plant height and physiological traits had a high impact under stress environment. Cluster analysis of families based on all of traits for two environments defined desirable clusters. This cluster divided families into five groups each of which desirable for a particular trait such as high or low grain yield in stress environments, early maturity, late maturity, high RWC and high ELWR.

Keywords: Durum wheat, drought stress, grain yield, morpho-physiological traits.