Acclimation of Ecophysiological and Agronomic Traits to Increasing Growth Temperature in Three Cowpea Genotypes Grown in Anuradhapura, Sri Lanka

The future of food crop production is uncertain due to the negative effects of global warming. Cowpea is grown in warm environments including in Sri Lanka, where less is known about the potential acclimation of ecophysiological and agronomic traits to increasing temperatures. We evaluated the acclimation potential of yield components and ecophysiological traits of three recommended cowpea genotypes to the seasonal variation in growth temperature in Anuradhapura, Sri Lanka. This study was conducted at the Faculty of Agriculture, Rajarata University of Sri Lanka, in two consecutive seasons with average daytime temperatures of 30.4°C and 33.2°C. Three genotypes, Dhawala, Waruni, and MI-35, were tested in this study, and their rates of leaf photosynthesis and respiration at the 50% flowering stage and final yield parameters were measured at their respective average growth temperatures in both seasons. The total yield per hectare showed an average decrease of 16%, 17%, and 22% in the Dhawala, Waruni, and MI-35 genotypes at high average growth temperature, respectively. These reductions were associated with the reduction in the number of seeds per pod, hundred seed weight, and number of pods per plant, suggesting that there could be an among-genotype variation in flower abscission, fertilization, and biomass partitioning during the season in which the average growth temperature was high. In the season with high average growth temperature, genotype Dhawala showed an increased carbon gain per unit carbon loss and increased water use efficiency compared to MI-35 and Waruni genotypes. Therefore, genotype Dhawala is a better candidate than MI-35 and Waruni genotypes in the face of global warming, which may be considered in further breeding programs and market preferences. More work is proposed to examine the patterns of biomass partitioning and radiation use efficiency in three cowpea genotypes at elevated temperatures.