SALINITY-INDUCED ANTIOXIDANT ENZYME SYSTEM IN MUNGBEAN [VIGNA RADIATA (L.) WILCZEK] CV.) GENOTYPES

Salt stress poses a serious challenge to plant growth and development and hence influences the yield and crop productivity. This study investigates the impact of exogenous sodium chloride (NaC1) on the seedlings of six genotypes of mungbean [Vigna radiata (L.) Wilczek] with reference to the status of a stress indicator (hydrogen peroxide: H2O2) and some antioxidant enzymes, viz. superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), glutathione reductase (GR), glutathione peroxidase (GPX) and glutathione-S-transferase (GST). Ten-day-old seedlings were subjected to salt stress (0-250 mM) given in split application along with the half strength Hoaglands. The salt stress increased the H2O2 production in a concentration-dependent manner up to 250mM NaC1 in all genotypes. NaC1 levels were positively correlated with the production of hydrogen peroxide in leaves as evidenced by the 3, 3-diaminobenzidine (DAB)-mediated tissue fingerprinting. The activity of SOD, CAT, APX, GR, GPX and GST increased significantly upon the NaC1 treatments and attained its maximum at 150mM for SOD and CAT, at 200mM for APX, GR and GST and at 250mM for GPX. The pattern of increase in the activity was similar in all the genotypes studied, though the quantitative levels were markedly different. The oxidative stress due to H2O2 generationand the antioxidant enzymes activity to combat it may serve as the screening markers for selecting the stress-tolerant genotypes of mungbean.