Evaluation of cowpea varieties and hybrids tolerance to water deficit during vegetative and reproductive phases

Cowpea (Vigna unguiculata L. Walp) is one of Benin’s most cultivated and consumed grain legumes. However, drought remains one of the main causes of its decline in yield. The aim of this work was to identify superior cowpea genotypes tolerant to water deficit. Twenty-six (N = 26) genotypes (varieties and hybrids) were subjected to two water regime conditions (well-watered and stressed) in a greenhouse at the International Institute of Tropical Agriculture (IITA), Benin) during the 2021 dry season. The experiment was laid out in a split plot with 3 replicates. The results showed that proline content, chlorophyll content, number of pods per plant, number of seeds per pod, hundred-seed weight and seed yield were all significantly (P < 0.001) reduced under the effect of water deficit. However, the genotypes KVX396-18, Kpodjiguèguè x KVX 396-18, IT97K-206-1-1, IT99K573-1-1, IT07K-211-1-8 x IT97K-206-1-1, and F2_Kpodjiguèguè x Tawa provided the highest values under water deficit compared to unstressed plants which served as controls. These genotypes were the best water deficit tolerant and high-yielding genotypes. Low values were recorded for F2_ genotypes KVX61-1 x Tawa, IT07K-211-1-8 x Tawa, KVX61-1, IT07K-211-1-8 x IT99K-573-1-1, F2_IT07K-211-1-8 x IT99K-573-1-1, F2_IT06K242-3 x IT97K-206-1-1, KVX61-1 x Tawa, which are considered in this case as drought-sensitive and low-yielding genotypes. A correlation between plant height, leaf width, pod maturity days, pod length, number of pods per plant, and hundred seed weight and yield were observed. Number of pods per plant (NPP), grain yield per plant (GYP), hundred seed weight (100WS), pod length (PL), number of days to pod maturity (NDPM), number of seeds per pod (NSP), and number of leaves per plant (NLP) can therefore be exploited in cowpea breeding programs to improve yield and drought tolerance in susceptible and low-yielding genotypes.