Physiological responses and expression of VrDREB2A gene at different growth stages of mungbean (Vigna radiata L. Wilczek) under drought stress
Abstract Mungbean is an important pulse crop and commonly grown in Asia. Drought affects mungbean growth and yield at at different growing stages and various levels through physiological traits and gene expression. In this study, two mungbean cultivars, DX208 and Tam Thanh Hoa, were exposed to drought at the vegetative and flowering stages and assessed for various morphophysiological traits at 8, 12, 15 and 15 days post withholding water and the plant recovery 7 days after re-watering. Differential expression of VrDREB2A gene was observed in leaf and root of two mungbean cultivars under drought condition. Plants used up water more quickly at the flowering stage than the vegetative stage. Drought adversely affected the plant height, leaf number, above-ground plant biomass and root weight with relative reduction to the control by 4.0–85%. Yield components and individual yield reduced significantly by around 50–60% compared to the control. Relative expression of VrDREB2A gene was varied, with stronger expression in leaves and roots when drought imposed at the flowering and vegetative stages respectively. Increase in VrDREB2A expression occurred earlier at 8 days compared with 12 days for drought imposed at the flowering and vegetative stages respectively, resulting in more tolerance of plants to drought at the flowering stage. The results indicate that VrDREB2A functioned as an important transcriptional activator and might help increase the drought stress tolerance of the mungbean plant at various growing stages. Morphophysiological traits can also be used as indicators in screening mungbean for drought tolerance.