Abstract: Study of the physiological reactions of wild wheat relatives to drought stress can help to identify the effective mechanisms of drought tolerant. Therefore, in an experiment, the physiological response of 125 wild diploid wheat genotypes of Aegilops tauschii under rain-fed and supplemental irrigation conditions was studied. Physiological traits including Relative Water Content of leaves (RWC), Excised Leaf Water Retention (ELWR), Relative Water Loos (RWL), chlorophyll a, chlorophyll b, total chlorophyll, carotenoids, ion leakage, membrane stability index (MSI) and proline content was measured. The results showed that increasing proline production and reducing chlorophyll degradation and low rate of the Membrane Stability Index (MSI) could help to increase yield under rain-fed conditions. It was also found that the lower ion leakage and the low cell membrane damage led to the higher yield in rain-fed conditions. The results of regression analysis in both rain-fed and supplemental irrigation conditions showed that proline content and total chlorophyll were introduced into the model, and justified the most changes in grain yield. In genotypes. 16, 22, 43, 66 and 106 (these genotypes from the regions of Iran-Astara, Iran- unknown, Iran-Rezvanshahr, Iran-Ramsar) are resistant genotypes. Key words: Cluster analysis, Drought stress, Principal component, Regression analysis, Wild wheat.
