Root and Leaf Traits for Dehydration Avoidance and Enhanced Grain Yield in Cowpea (Vigna unguiculata L., Fabaceae) Under Drought.

Drought stress, which is exacerbated by climate change, is a major contributor to crop production losses in rainfed agriculture. Two genotypes of cowpea (Vigna unguiculata, (L.) Walp.) with determinate (IT-16) and indeterminate (IT-96D-610) growth patterns were grown either well-watered or subjected to drought stress at vegetative and flowering stages in a pot experiment in a glasshouse. Stomatal conductance (gs) and soil moisture were measured daily during the drought stress periods, while chlorophyll fluorescence data were collected every third day. Both genotypes maintained relatively high-water content (RWC > 80%), indicating dehydration avoidance; however, IT-96D-610 consistently maintained a higher RWC than IT-16. Under drought stress, IT-96D-610 exhibited lower gs and less sensitive stomata, greater total root length, root surface area and a higher root-to-shoot ratio compared to IT-16. These traits were associated with higher seed yield and water productivity in IT-96D-610 than in IT-16. In contrast to IT-96D-610, genotype IT-16 showed higher photosynthetic efficiency, indicated by higher Fq'/Fm' and qP, and produced more biomass, but with reduced grain yield. This study underscores the importance of selecting traits for dehydration avoidance, such as RWC, deep-fine roots and moderated stomatal conductance, in cowpea breeding programs aimed at improving productivity under drought conditions.