Research PaperGenotypic variability for tolerance to high temperature stress at reproductive phase in Mungbean [Vigna radiata (L.) Wilczek]

•The high temperature treatments significantly reduced dry matter production and grain yield of mungbean genotypes.•Plants subjected to heat acclimation treatment prior to high temperature showed better performance than plants directly subjected to high temperature treatment.•Viable pollen number was directly related to pod number (r2 = 0.55**) and grain yield (r2 = 0.62**) on per plant basis.•Pollen viability and membrane integrity could be used rapid as tools to assess genetic variation in mungbean genotypes.•The study identified genotypes tolerant and susceptible to high temperature for further research.

This study investigated variation in 28 mungbean genotypes in their response to high temperature with 45/30 °C (NAc-HT) imposed at the reproductive phase, and to prior-acclimation of plants to elevated temperatures at 35/28 °C before subjecting them to high temperatures (Ac-HT). Environmentally controlled growth chambers (ECGC) were used to assess the impact of high temperatures on crop growth, reproductive development and yield. The mean shoot dry matter was reduced by 21% and 24%, with grain yield by 56% and 59% in Ac-HT and NAc-HT treatments, respectively, compared to control (CON). There was significant genotypic variation in dry matter and yield (P > 0.001) for temperature treatments. The mean total pollen number was reduced from 88/mm2 in CON to less than 50 in Ac-HT and 40/mm2 in NAc-HT treatments, with significant genotypic variation. The mean ratio of viable pollen to total pollen was 83%, 74% and 40% in CON, Ac-HT and NAc-HT treatments, respectively, suggesting that acclimated plants (Ac-HT) were able to maintain higher pollen viability than non-acclimated plants (NAc-HT). The viable pollen number was linearly related to pod number (r2 = 0.55**) and grain yield (r2 = 0.62**) on a per plant basis. Based on shoot biomass, grain yield and other physiological parameters, genotypes were grouped as tolerant or susceptible, for further studies.