Growth responses and differential expression of VrDREB2A gene at different growth stages of mungbean ( Vigna radiata L. Wilczek) under drought stress

Mungbean is an important pulse crop and is predominantly cultivated across Asia. However, its production is hampered by climate change-induced drought stress. Drought affects various morpho-physiological processes associated with growth and molecular functions. This study analyzed growth responses and VrDREB2A gene expression in two mungbean cultivars, DX208 and Tam Thanh Hoa under water deficit at vegetative and flowering stages. Water use and growth characters were evaluated at four time-points (8, 12, 15 and 20-day drought) and 7-day recovery while yield components and yield were recorded after harvesting. Differential expression of VrDREB2A gene was analyzed at four time-points for leaf and root. Plants used up water more quickly at the flowering stage than vegetative stage. The data for plant height, leaf number, above-ground plant biomass and root weight indicated that drought stress significantly repressed mungbean growth, with a reduction relative to the control by 4.0–85%. Yield components and individual yield reduced significantly by 50–60%, with more reduction in drought imposed under the vegetative stage. VrDREB2A expression began to increase on a 12-day drought and was significant in stressed roots on a 20-day drought at the vegetative stage. In contrast, an increase in VrDREB2A expression occurred from 8-day and lasted until a 20-day drought in stressed leave and root at the flowering stage. Overall, the vegetative stage was more sensitive to drought than the flowering stage. A cultivar with less relative reduction in growth and yield related traits and higher VrDREB2A expression was more tolerant to drought. VrDREB2A functioned as an important transcriptional activator and can increase the drought stress tolerance of the mungbean.