Physiological Divergence in Green Gram [Vigna radiata (L.) Wilczek] Genotypes for Drought and High Temperature Stress Tolerance During Flowering Phase

Background: Drought and high temperature stress limits the crop production. Development of drought and high temperature tolerant cultivars that can withstand and yield better under adverse conditions is very much important to ensure the food and nutritional security. Green gram is one of the important pulse crops with high nutritional and economic value. Among the various stages of plant growth and development, reproductive stage is highly sensitive to drought and high temperature stress across all species. The main objective of this study was to evaluate green gram germplasm collection and identification of elite greengram genotypes that can withstand drought and high temperature stresses at reproductive stage. Methods: The experiment was conducted during March-April, 2019, at National Pulses Research Centre, Vamban, Pudukottai district, Tamil Nadu. To study the influence of combined drought and high temperature stress during reproductive stage, the green gram genotypes were sown in pots. Six pots were maintained for each genotype of which three were maintained at 100% field capacity (control) and for another three; drought stress (50% field capacity for 5 days) was imposed combined with high temperature stress (36 +/- 2 degrees C) during reproductive phase (35 Days after sowing). At the end of stress period, physiological and biochemical analysis were carried out to identify the tolerant green gram genotypes against drought and high temperature stresses. Result: In the present study, drought and high temperature stress has negative impact on green gram physiology. Among the genotypes screened for their tolerance at reproductive stage, the following green gram genotypes viz., TARM 1, VGG 15029, VGG 17003, VGG 17004, VGG 17006, VGG 17010 and VGG 17019 were found to withstand drought and high temperature stress and maintain high total chlorophyll content, relative water content and chlorophyll stability index. These green gram gramplasm can be used in pulse breeding program to evolve resilient green gram varieties. Screening of 29 green gram genotypes for drought and high temperature stress during reproductive stage were carried out by maintaining the drought stress (50% field capacity for 5 days) combined with high temperature stress (36 +/- 2 degrees C) during reproductive stage (35 days after sowing) by pot culture experiment. Total chlorophyll, relative water content, chlorophyll stability index (CSI), oxidants and antioxidant activity were quantified to identify the tolerant green gram genotypes against drought and high temperature stresses. Based on physiological and biochemical parameters, the following green gram genotypes viz., TARM 1, VGG 15029, VGG 17003, VGG 17004, VGG 17006, VGG 17010 and VGG 17019 were found to withstand and tolerate combined drought and high temperature stresses at flowering stage.