Comparative response of annual Medicago spp. to salinity

Abstract

The present study was conducted to evaluate the morphological and physiological traits and the expression profile of antioxidant genes in four annual Medicago genotypes (M. truncatula Karaj; M. truncatula Qom; M. polymorpha; M. laciniata) under salinity. The experiment was carried out in a randomized complete block design, in which salinity (0 and 100 mM NaCl) allotted to main plots and genotypes assigned to subplots. The results indicated that salinity significantly increased Na+ content and decreased K+ content thereby increased the ratio of Na+/K+ in all annual Medicago genotypes. Salinity caused reduction in dry weight of shoot and root in all plants. Total chlorophyll and carotenoid contents declined by virtue of salt stress and such reduction was more remarkable in M. truncatula compared to M. polymorpha and M. laciniata. In a reverse manner, salinity increased anthocyanin content in all Medicago genotypes. Salinity augmented the overexpression of glutathione S-transferase (GST), glyoxalase I (GLXI), glutaredoxin (GRX), and peroxidase (PERX) genes in annual Medicago genotypes. Nevertheless, the overexpression of GLXI, GRX, and PERX genes was greater in M. truncatula plants than in M. polymorpha and M. laciniata plants. The expression of antioxidant’s genes in M. polymorpha and M. laciniata plants was greater than in M. truncatula and M. truncatula plants. In conclusion, M. polymorpha and M. laciniata were regarded as salt-tolerant species by less reduction in chlorophyll and carotenoid contents, less increase in anthocyanin content, and higher expression of GLXI, GRX, and PERX.