Salicylic Acid- and Ascorbic Acid-Induced Salt Tolerance in Mung bean (Vigna radiata (L.) Wilczek) Accompanied by Oxidative Defense Mechanisms

The present study aimed at investigating the physiochemical role of phytoprotectants, i.e., salicylic acid (SA) and ascorbic acid (AsA), to induce salt tolerance (0, 80 mM NaCl) in two indigenous mung bean varieties, viz. NM-92 (salt tolerant) and NM-28 (salt sensitive). The mung bean varieties were exposed to salinity stress (80 mM NaCl) after 1 week of germination and then exogenously sprayed with different levels of SA and AsA (0, 50, 100, 150 mg L-1) on appearance of stress symptoms. The experiment was carried out in a completely randomized design with three replications. Salinity stress significantly reduced the growth attributes and photosynthetic pigments and considerably increased electrolyte leakage (92-94%), lipoxygenase activity (113-152%), malondialdehyde (103-105%), and hydrogen peroxide (44-46%) contents. Treatment of control plants (0 mM NaCl) with SA or ASA did not significantly reduce growth attributes and photosynthetic pigments. However, exogenous SA and AsA (0, 50, 100, 150 mg L-1) markedly enhanced salt stress tolerance by reducing electrolyte leakage (26-34%), lipoxygenase activities (45-51%), and malondialdehyde (32-37%) and hydrogen peroxide concentration (17.2-17.5%) due to higher accumulation of stress metabolites and antioxidative enzymes. The highest increase in stress tolerance was recorded by foliar application of (100 mg L-1 SA) in NM-92. We conclude that application of 100 mg L-1 SA is an effective approach to increase salt tolerance in mung bean. Moreover, the cultivation of salt-tolerant cultivars such as NM-92 is recommended to obtain better mung bean yields in salt-affected areas.