Effect of Drought Stress on Antioxidant Enzymes Activities, Proline Content and Some Morghological Traits in Different Castor Bean Ecotypes (Ricinus Communis L.)

Drought is one of the most serious threats in agricultural production worldwide, and climate change is likely to exacerbate this threat. In order to evaluate the drought tolerance of different castor ecotypes, a factorial experiment was conducted in a completely randomized design with three replications in Sari Agricultural Sciences and Natural Resources University. The first factor was 22 castor ecotypes and the second factor was drought stress with 5 levels, full irrigation, four levels (irrigation was cuted at the primary of spike growth) (11, 22, 33, 44 days after Irrigation cut off). Experimental traits were included the activity of the antioxidant enzymes Catalase, Guaiacol peroxidase and Ascorbate peroxidase, the biochemical activity of Malondialdehyde (MDA), Proline content, Plant height, stem diameter and number of leaves. Cluster analysis classified the ecotypes into three clusters under normal and drought stress conditions.The results showed that the activity of Catalase, Ascorbate peroxidase, Guaiacol peroxidase, Malondialdehyde and Proline content under drought stress conditions of the third group (Tolerant) compared to the first group (Sensitive) were increased 81.5, 81.87, 70.27, 80.05, 81.87, respectively. On the other hand, the differences between tolerant and sensitive groups at stress conditions in plant height, stem diameter and number of leaves were 74.74, 80.50 and 83.38%, respectively. The highest correlation under drought stress conditions was observed between Catalase and Ascorbate peroxidase (r = 0.997) and the lowest non-significant correlation was observed between proline and plant height (r = 0.292). According to the results, in terms of the studied traits 5 and 19 ecotypes were introduced as drought tolerant ecotypes.