Water Stress Tolerance at Different Growth Stages in Cowpea [Vigna unguiculata (L.) Walp.] in the Far North Region of Cameroon

Abstract

Background: Cowpea is a protein-rich legume essential for food security in sub-Saharan Africa, but its productivity is increasingly constrained by drought and irregular rainfall patterns. Objective: To address intra-seasonal drought episodes when they occur at critical stages of the crop and to mitigate the resulting decline in yield in Cameroon, it is necessary to identify and understand the mechanisms of water-stress tolerance in accessions at different stages of their growth cycle. Methodology: One hundred and seventy-three cowpea accessions and one control variety were evaluated under two factors (genotype and developmental stage) for their response to different water conditions. The agro-morphological and physiological parameters of the plants were assessed per bag in a randomized complete block design with three replications. An intermittent water-deficit treatment covering both the vegetative and reproductive stages was studied. Results and Discussion: The results show that water stress negatively affects agro-morphological and physiological variables, considerably reducing their performance, and that its effect is more noticeable during the second water stress. Nevertheless, water stress caused a greater increase in chlorophyll content in the majority of accessions during the second water stress (SH2), from the vegetative stage to flowering, which led to a decrease in final productivity because of their inability to manage light energy (photoinhibition). Accessions A161, A108, A106, A1 and A151 proved to be accessions of choice in terms of pod production, seed production, root size per plant and water-stress tolerance. Accessions A12, A45, A93, A105, A146 and A167 also proved to be accessions of choice in terms of greenness, recovery rate, chlorophyll content and water-stress tolerance, outperforming the control variety A140 in performance. The identification of these accessions could be used in breeding programs to improve cowpea tolerance at the vegetative and/or reproductive stages and could help increase yield. Conclusion: Based on yield-related traits, root length and responses to water deficit, the study revealed that accessions A161, A108, A106, A1 and A151 were identified as promising drought-tolerant accessions.