Phenotyping diverse cowpea genotypes reveals shoot traits contributions to drought recovery

Abstract The success of a breeding program largely depends on the presence of sufficient genetic diversity in crops to provide an avenue for selection of desirable genotypes for utilization in crop improvement. However, the primary gene pools of many crop plants are so depleted in genetic variability which is a consequence of continuous selections imposed by plant breeders. This necessitates exploring the potentials of landraces for sources of resistance to biotic and abiotic stresses. Thus, the “Wooden box techniques” was adopted to screen cowpea genotypes for their response to seedling drought stress, owing to its rapid and high throughput nature. Here, 420 cowpea genotypes were evaluated for their tolerance to seedling drought. Time course analysis of growth and agronomic traits revealed gradual cessation of growth as drought stress intensified as evidenced by reduction in trifoliate number, increase in leaf senescence and stem wilting. Multivariate analysis using principal component (PC) analysis and k-mean clustering identified 3 major clusters where PC1 and PC2 explained 46.7% of the variability in response to drought stress. The biplot analysis showed that plant height, stem greenness and trifoliate number contributed positively to PC1 while leaf senescence score was negatively related to the clustering on this axis. The comprehensive data analysis pipeline allows us to identify the relationship between the agronomic and stay-green parameters, which provides us with the understanding of traits that could be useful during the selection of lines under drought stress at the seedling stage. Our method provides an aid-to-selection for rapid screening of a large collection of cowpea lines for their response to seedling drought stress. Additionally, our results identified potential tolerant genotypes for use as parents for genetic analysis of drought tolerant traits and incorporation into breeding programs targeting the development and deployment of drought tolerant varieties.