Role of Antioxidative Defense in Yellow Mosaic Disease Resistance in Black Gram [Vigna mungo (L.) Hepper]

Yellow mosaic virus (YMV) transmitted by whitefly (Bemisia tabaci) causes yellow mosaic disease (YMD) in blackgram cultivars only during kharif season but disease was not observed in the same cultivars sown during spring season. The main objective of the present investigation was to study the cooperative role of various antioxidative enzymes such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPOX), glutathione reductase (GR), monodehydro ascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) along with non- enzymic antioxidants and free radical scavenging activities under natural epiphytotic disease conditions in black gram cultivars during kharif and spring season. Three black gram cultivars-KUG253 (highly susceptible to YMD), MASH114 (resistant) and Cross (KUG253 × MASH114) at F5 generation were sown during both the seasons. During the kharif season, YMV caused severe chlorosis only in KUG253 cultivar at 40 days after sowing (DAS) which affected its quantum efficiency by 58% as compared to the spring season. Higher specific activities of MDHAR, DHAR, and GR in Cross and MASH114 cultivars during kharif season at 20DAS might have helped these cultivars to fight off YMV right from the beginning of the infection. Cross cultivar showed the highest superoxide anion scavenging activity (SASA), ferric reducing antioxidant power (FRAP), 2,2-diphenyl-1-picryl hydrazyl (DPPH) free radical scavenging activity and total reducing power (TRP). On the other hand, KUG253 cultivar struggled to maintain the specific activity of CAT, GR, and DHAR as the disease progressed further. GPOX and APX enzymes might have tried to compensate for the loss of CAT enzyme but high specific activity of NADPH Oxidase promoted the production of harmful ROS which ultimately lead to higher oxidative damage in KUG253 cultivar.