Physiological markers may provide a shortcut for identifying drought tolerance in alfalfa ( Medicago sativa L.). Thus, the objective of this study was to understand physiological properties of alfalfa to assess drought tolerance of its cultivars. Ten alfalfa cultivars (Qomi, Isfahani, Hamedani, Bami, Ordobadi, Gharayonje, Nikshahri, Yazdi, Baghdadi, and Cody) and four irrigation regimes (55, 65, 75, and 85% depletion of available soil water) were arranged as split plot in a completely randomized block design with three replications to determine the chlorophyll, carotenoid, soluble sugars, proline, relative water contents, and herbage yield response of alfalfa cultivars to drought stress. Physiological and herbage yield traits were drought level-cultivar-specific and discriminated the cultivars based on their drought tolerance. Based on the correlation between drought tolerance and measured traits at the highest drought level, carotenoid content ( r=0.94), was the most important marker followed by relative water content ( r=0.92) and soluble sugars content ( r=0.89), respectively, and Baghdadi was the most drought tolerant cultivar. The results showed that the physiological markers may be used to identify alfalfa germplasms for drought tolerance.
