Physiological Responses of Chickpea Genotypes to Cold and Heat Stress in Flowering Stage

Due to climate change, more temperature extremes are expected in the future, potentially endangering agricultural production. Chickpea (<i>Cicer arietinum</i> L.) is an important cool-season food legume grown worldwide; however, cold and heat episodes are major threats in chickpea production that cause considerable yield losses especially at the flowering stage. The aim of this study was to evaluate the physiological performance of contrasting chickpea genotypes during the flowering phase under cold and heat. Four chickpea genotypes (Desi, Eldorado, Acc#2 and Acc#7) with different temperature susceptibilities were treated for 3 days under cold (9/4 °C) and heat (38/33 °C). The results showed that cold stress reduced the maximum quantum efficiency of photosystem II (F_v/F_m) by 5%, net photosynthetic rate (P_N) by 74%, and chlorophyll a+b content by 31% on average in all tested genotypes. Up to a 9-fold increase in the amount of starch was found in the leaves of plants under cold stress, indicating that carbohydrates strongly accumulated in chickpeas under cold stress. This helps to maintain the vegetative and generative organs and enable fast recovery. Under heat stress, chickpeas maintained F_v/F_m and P_N, although chlorophyll a+b content decreased by 39% on average. Carbohydrates did not accumulate under heat in chickpeas; thereby, a reduction in biomass and reproductive organs took place. Genetic variation in response to cold and heat stress was detected among the tested flowering chickpea genotypes. Desi and Acc#2 were cold-sensitive candidates, and Eldorado was a cold-tolerant candidate, whereas Acc#7 and Acc#2 were heat-sensitive candidates, while Desi and Eldorado were heat-tolerant candidates. This study provides important knowledge on the physiological response of flowering chickpeas under cold and heat stress. This will benefit the identification of stress-tolerant chickpea genotypes to ensure high yields in the future climate.