Response of physiological traits to drought stress in some populations of sainfoin (Onobrychis viciifolia)

This study was conducted to evaluate the response of physiological traits of sainfoin to drought stress and to identify drought tolerant populations in a sainfoin collection from Iran. Ten populations were evaluated over two harvests according to a split plot in time design under normal and drought stress conditions. Analysis of variance showed significant difference among sainfoin cultivars for all the measured traits except for chlorophyll a/b ratio and carotenoids content. Drought stress significantly increased proline content while forage yield and other traits were considerably decreased. Under normal moisture condition Fereidonshahr2 and Khansar2 with average values of 37 and 34 ton/ha had the highest forage dry matter yield while in stress condition Isfahan, Fereidonshahr2 and Kerman cultivars produced more forage yield. Proline content increased more than 600 percent under drought stress while relative water content and total chlorophyll content decreased 28 and 14 percent, respectively. The results of cluster analysis in both conditions separated cultivars into three groups identified as tolerant, moderately tolerant and susceptible, respectively. Tolerant cultivars could be used for future breeding studies in developing drought tolerant varieties.