Physiological evaluation of mungbean (Vigna radiata (l.) Wilczek) cultivars for heat tolerance

Mungbean is adapted to relatively warm, dry climatic conditions of summer when day temperatures rise above 40°C during reproductive period which often results in substantial yield reduction. Therefore breeding for heat tolerance with improved yield had been a long term goal for mungbean vaietal improvement programme. The effect of heat stress during reproductive stage was investigated based on yield attributing traits, stress indices and growing degree days (^°Cd) in 20 high yielding mungbean cultivars released from different agro climatic zones of India. The cultivars were grown in Randomized Block Design with three replications in two environments, viz., non-stress environment (NSE) (15^th July sowing) and heat-stress environment (HSE) (7^th April sowing). It was seen that genotypic differences and genotype × environment interactions were significant for all the characters. Among the cultivars studied, three cultivars viz., Samrat, IPM 02-3 and IPM 2–14 were identified as the heat tolerant cultivars as indicated by their low heat susceptibility index. The thermal time (Growing degree days, ^°Cd) to reach mean cropgrowthdurationwas 1662°Cd under NSE while, itwas 1471°Cd under HSE.