Abstract Emmer wheat (Triticum turgidum subsp. dicoccum), as the early ancestors of bread wheat and durum wheat, is one of the essential genetic resources for durum wheat breeding. It can be used as one of the most promising genetic sources for improving drought and salinity tolerance and increasing durum wheat grain quality. This research was carried out to study genetics and eva‎luate drought tolerance in F5 generation lines produced from the crossing of eight durum and four emmer wheat in a diallel fashion. The 66 F5 lines (direct crosses) with the 12 parental lines were eva‎luated under two irrigation regimes of non-stress (50% soil moisture depletion) and water-stress (90% soil moisture depletion) environments in the form of a simple lattice design with two repetitions. The results of the combined analysis of variance showed a significant difference (P<0/01) among all the genotypes (parents and their offspring) for all the eva‎luated traits and for many important yield and yield component traits indicating significant genetic diversity between parents and their offspring. The effect of the water environment and the genotype × environment interaction was significant for most traits, suggesting a high genetic diversity created by crossing the two wheat subspecies. The transfer of adaptation genes from emmer wheat to durum wheat caused increased resistance and improved breeding traits under adverse environmental conditions. By comparing averages of traits, it was observed that water stress decreased most of the traits except days to booting, days to spike emergence, days to flowering, grain hardness, and proline content in both moisture environments. It was also observed that the lines obtained from crossing durum × emmer had a high variation for the traits of peduncle length, spike length, plant height, biological yield, grain yield, harvest index, 1000 grain weight, test weight, Zeleny index, grain protein, grain hardness and water absorption of flour in both moisture environments. This research observed the highest correlation coefficients between grain yield with harvest index and days to spike at water stress conditions (-0.73) and test weight at normal irrigation conditions (71. 0). In both moisture conditions, there was a positive and significant correlation between grain yield with 1000 grain weight, biological yield, harvest index, and test weight. Principal components analysis revealed two main factors, displaying 88.62 and 56.91 percent of the total variation at normal and water stress conditions. Also, all F5 families were segregated into five distinctive groups, including durum parents, durum × durum crosses, durum × emmer crosses, emmer × emmer crosses, and emmer parents. Correlation results between drought resistance indices with grain yield under normal irrigation and water stress conditions showed that STI, MP, and GMP indices are suitable for selecting genotypes with high grain yield at both moisture conditions. According to the graphs drawn for drought tolerance indices (STI, MP, and GMP) versus grain yield under both moisture conditions, genotypes 17, 19, 26, 37, and 45 from the group of durum × durum crosses and genotypes 23, 32, and 22 from the group of durum × emmer crosses, were recognized as high- grain yielding genotypes in both moisture conditions. Therefore, they were assumed to be more tolerant to water stress and identified as drought-tolerant genotypes. The results of this research presented that the generations created from the crossing of tetraploid wheat subspecies are valuable sources of diversity of important agricultural and qualitative traits and provide a way for breeders to improve and produce drought-tolerant

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محمدرضا سبزعليان دستجردي , مهديه غلامي