Drought stress is a serious threat to plant growth and to crop production in many areas of the world. Under such conditions, increasing genetic diversity and then utilizing it in the selection of the best-adapted plant material can be a useful strategy. In this study,31 synthetic hexaploid wheat genotypes were evaluated in field as well as in laboratory experiments.Significant differences were observed among the synthetic lines for most traits in either stress or non-stress conditions. Most traits were negetively affected by drought stress, the highest reduction being observed in grain yield.The results of stepwise regression analysis showed that traits such as spike weight, days to flowering, ear length and number of fertile spikelets per spike could be used as desirable criteria for yield improvement under drought stress,whereas seed per spike,1000-kernel weight and ear weight could be used in treatments under non-stress conditions. Most variations among traits were accounted for by 6 and 5 traits in stress and non-stress conditions respectively. Among the drought resistance indicies,Mean Productivity (MP),Geometric Mean Productivity (GMP) and Stress Tolerance Index (STI) were the most suitable ones for drought resistance selection. Regarding bi-plot display, control line Mahdavi and synthetic genotypes 2 and 4 were the most resistant lines. Resultes of PEG experimant in laboratory indicated significant differences among lines for germination rate and coleoptyle length, although they did not show any significant correlation with drought resistance indices.
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