Effect of drought Stress on Yield and yield components and Determination of the Best drought Stress Index in Common Bean (Phaseolus vulgaris L.)

The effect of drought on the seed yield and some associated characteristics of common been under normal and drought stress conditions and determination of durable genotypes to drought were studied by planting 32 genotypes in two separate augmented designs in normal and stress conditions. These genotypes were evaluated in randomized complete block design with 3 replications in the field of faculty of Agriculture, university of Tehran in Karaj in 2007. Analysis of variance showed that there were significant differences among varieties in all traits, indicating the existence of genetic variation among varieties. Heritability, genotypic and phenotypic coefficients of variation were determined. Most of the measured traits had significant genotypic coefficient of variation. In normal and stress conditions, yield was highly correlated with the weight of pods in plant. Also, The results of stepwise regression showed that, selection can be done based on weight of pods in plant, harvest index, number of seed in pod and 100 seed weight. In the classification of genotypes based on yield and their component using cluster analysis (UPGMA), all of the genotypes were classified in 6 and 5 separate groups in non stress and stress conditions, respectively. Comparison of different durable to drought indices showed that Stress Tolerance Index, Geometric Mean Productivity and Harmonic mean, were the best indices that can be used to determine durable genotypes. Based on result of by-plot analysis, 9, 4, 13, 15, 16, 14 and 21 genotypes were recognized as high- yielding genotypes under both stress and normal conditions.