Simultaneous exposure of contrasting Vigna radiata cultivars to Macrophomina phaseolina infection and drought stress: morpho-physiological and biochemical implications

Drought is a major abiotic stress which affects the growth and yield of crops globally. The infection caused by Macrophomina phaseolina is a significant limiting factor in the Vigna radiata (mungbean) production inflicting up to 100% yield losses under dry and hot conditions. In the present study, two cultivars of mungbean viz. RMG-492 and IPM 02-14 were exposed to combined M. phaseolina infection and drought stress. The cultivar RMG-492 was relatively more tolerant to M. phaseolina infection than IPM 02-14. There was reduction in disease incidence in plants exposed to combined stress in both the cultivars. However, a remarkable decrease in root rot (13.33%) and crown rot (20%) was observed in "IPM 02-14." This could be accredited to a stronger defense response including increased antioxidant capacity and lignin deposition in dual stress treated plants. Moreover, differences were observed on comparing the stress response in leaves upon fungal infection under well-watered and water-deficit conditions. The salicylic acid played a significant role in fungal stress response. However, soluble sugar mediated regulation was prominent in combined stress. Therefore, it could be concluded that plants adopt distinct response strategies under combined stress which could be further exploited to produce multiple stress resistant crops.