Journal of Crop Breeding

In order to evaluate drought resistance indices, an experiment was carried out in a randomized complete block design in three replications with thirteen bread wheat genotypes and two levels of irrigation, stressed and non stressed, at Dry land Agricultural Research Institute (DARI), Maragheh, in 2009-2010. tolerant on the basis of yield performance in stressed (y_s) and non-stressed (y_p) environments, quantitative measures of drought tolerance such as mean productivity (MP), tolerance index (TOL), geometric mean productivity (GMP), harmonic mean (HM), stress susceptibility index (SSI) and stress tolerance index (STI), were calculated. The Analysis of variance showed that the highest potential and stress yield were related to the genotypes 4 and 12, respectively. The highest stress tolerance index (STI), mean productivity (MP), tolerance index (TOL), geometric mean productivity (GMP) and harmonic mean (HM) were related to the genotypes 4, 6 and 1. In both stressed and non-stressed conditions, correlation analysis between yield and all indices revealed that STI is the best indice for screening of drought tolerant genotypes. Cluster analysis for yield in stressed (y_s) and non-stressed (y_p) environments and grouped drought tolerance quantitative indices in three groups. Factor analysis based on principal component analysis method indicated that two important factors justified 99.9 (first factor assigned 74.26% and two factor assigned 25.64%) percent of the total variation among traits in drought and non-drought stress conditions.