Tolerance to water deficit in cowpea populations resulting from breeding program: detection by gas exchange and chlorophyll fluorescence

Abstract

Cowpea is a crop that exercises social, economic and nutritional importance on the population of several countries due to grain production. This study aimed to (1) evaluate the effect of water deficit stress on gas exchange and chlorophyll fluorescence parameters in six populations, and (2) identify the better population to select plants for tolerance to water deficit stress, derived from crosses of the cowpea cultivars cultivated under irrigation and water deficit conditions. The experimental design was completely randomized composed of six populations, with two parents P1 and P2, and F1, F2, BC1 and BC2 generations derived from the cross between BR3-Tracuateua (sensitive to drought) and Pingo de ouro-1-2 (tolerant to drought). F2 generations showed higher values of net photosynthetic rate, stomatal conductance and water-use efficiency when these populations were exposed to water deficit. In case of chlorophyll fluorescence parameters under water deficit stress, F2 populations showed better results for effective quantum yield of PSII, photochemical quenching and apparent electron-transport rate, while lower values of non-photochemical quenching, relative energy excess at the PSII level and ratio between the apparent electron-transport rate and net photosynthetic rate. Our results on gas exchange and chlorophyll fluorescence revealed that the better performance under water deficit conditions was found in F2 generation, and this validated the breeding strategy used in this program aiming tolerance to water deficit, was successful.