Identification of drought-tolerant mung bean varieties based on germination, antioxidant, and osmolyte profiles

Drought stress severely impacts mung bean [Vigna radiata (L.) R. Wilczek] production, making exploration of drought tolerance and breeding strategies critical. This study investigated drought resistance mechanisms in ten mung bean cultivars under polyethylene glycol (PEG 6000)-induced water deficit, analyzing germination, morphology, and physiology. Drought impaired vigor index (VI) and seedling growth across all cultivars, with mung bean Bing 20 exhibiting reduced VI (76.28%) and seedling length (63.47%). Drought induced hydrogen peroxide (H₂O₂) bursts, exacerbating membrane lipid peroxidation and elevating malondialdehyde levels, wherein increased H₂O₂ content in Bing 18 (2.02-fold) and elevated malondialdehyde content in Bing 17 (36.64%). Mung bean activated superoxide dismutase, peroxidase, and catalase antioxidant enzymes to mitigate oxidative damage and enhanced seed vigor by upregulating amylase and osmolyte accumulation (soluble sugar, starch, soluble protein, and proline); α-amylase activity in Jin 8 was elevated by 1.68-fold, while Jin 1 exhibited increased starch (1.57-fold) and proline content (40.28-fold). Based on drought resistance coefficients derived from these traits, correlation and principal component analyses (PCA) were performed. Mung bean Jin 1, Jin 7, Jin 8, Bing 11, and Bing 18 were identified as relatively tolerant, whereas Bing 16, Bing 17, Bing 19, Bing 20, and Bing 21 exhibited greater susceptibility. Correlation analysis revealed contrasting metabolic strategies tolerant varieties prioritized rapid early growth, while susceptible varieties showed a complex balance of growth, defense, and osmotic adjustment. PCA identified germination index and seedling length as key drought resistance screening traits. These findings enhance understanding of drought tolerance and facilitate selection of varieties. HIGHLIGHTS: Drought tolerance of ten mung bean cultivars was comprehensively evaluated based on germination, morphological, and physiological profiles under PEG-induced stress. Distinct drought response strategies were revealed between tolerant (prioritizing rapid early growth) and susceptible (balancing growth, defense, and osmotic adjustment) mung bean varieties. Germination index and seedling length were identified as key indicators for screening drought-tolerant mung bean varieties.