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

This study investigated variation in 28 mungbean genotypes in their response to high temperature with 45/30 degrees C (NAc-HT) imposed at the reproductive phase, and to prior-acclimation of plants to elevated temperatures at 35/28 degrees 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/mm(2) in CON to less than 50 in Ac-HT and 40/mm(2) 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 (r(2) = 0.55**) and grain yield (r(2) = 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.