Evaluation of physiological and yield traits in cowpea for screening of drought tolerance lines

Drought (soil and/ atmospheric water deficit) is the most environmental constraints among abiotic stresses. Cowpea is inherently more drought tolerant than other vegetables, but it also suffers to a considerable yield loss when the moisture deficit is imposed during flowering and pod setting. The experiment was carried out at IIVR, Varanasi during spring-summer of 2012 and 2013. A total of 29 diverse cowpea genotypes, comprising of vegetable and grain types were selected for study. Drought stress was imposed 35 days after sowing by with holding the irrigation for 25 days. All genotypes were also kept under well watered control. Experimental findings revealed that under drought stress, some genotypes, viz., EC-30590, EC-37988, EC-390241, EC-15296, EC-472283 and Gomti expressed significantly higher relative leaf water content (>80%), photosynthesis (14.7 to 18.2 mu mol m(-2) s(-1)), stomatal conductance (0.443 to 0.818 mu mol m(-2) s(-1)), quantum yield of PSII photochemistry, i.e. Fvl Fm (0.467 to 0.727) and transpiration rate (0.0321 to 0.0467). These genotypes also showed less yield and dry matter reduction under drought stress as compared to susceptible cultivars/genotypes. The commercial cultivars such as, Akra Garima, Kashi Nidhi, Kashi Shyamal and Kashi Kanchan were found more susceptible to drought. It may concluded that genotypes EC-30590, EC-37988, EC-390241, EC-15296, EC-472283 and Gomti were fairly drought tolerant, and may be utilized for cultivation under water limited condition or for breeding of drought tolerant cultivars.