A Comparative Analysis on Morphological and Physiological Characteristics between Castor Varieties (Ricinus communis L.) under Salt Stress

Salt stress is one of the main abiotic factors affecting castor yield. Wild castor resources can provide important insights for cultivated castor breeding. However, little is known about how wild castor responds or adapts to salt stress. To understand the physiological mechanisms for salt tolerance in castor, the morphological and physiological responses of two varieties, wild and cultivated castor, with contrasted salt tolerance were characterized under salt stress. Seedlings were exposed to 0, 50, and 100 mM NaCl. The results showed that salt application significantly inhibited the increase in chlorophyll content and relative water content of cultivated castor. The degree of electrolyte leakage of wild castor under salt stress was significantly less than that of cultivated castor. In addition, the WT showed a lower content of reactive oxygen species (ROS) under the salt stress compared to CT. The activities of antioxidant enzymes like SOD, APX, GR, and MDHAR in the leaves of WT showed higher accumulation compared to those of CT under salt stress. The ratio of ASA/DHA and GSH/GSSG in leaves of WT showed a distinct increase compared to CT. In summary, our results revealed the salt stress resistance characteristics of wild castor. Wild castor also has the potential to be used as parental material in a breeding program. These results will be valuable for salt resistance breeding of cultivated castor.