Morpho-Physiological and Molecular Responses to Seedling-Stage Drought Stress in Different Cowpea Cultivars

Drought poses a significant challenge to cowpea growth and productivity, necessitating the development of drought-tolerant cultivars through detailed morpho-physiological and molecular analyses. This study evaluated drought stress responses in cowpea cultivars using polypropylene plastic boxes under greenhouse conditions. RT-qPCR was conducted to assess the relative expression of five photosynthetic and abiotic stress-related genes in a subset of seven contrasting cultivars at 7-, 14-, and 28-days post-treatment initiation (DPTI) and 24 h post-rewatering. Drought-stressed plants showed progressive wilting and a declining chlorophyll content, with plant greenness scores ranging from 2.2 (TVu11987) to 4.7 (TVu2428). California Blackeye (72.2%) and TVu11987 (69.4%) had the highest recovery rates, indicating greater drought tolerance, while TVu2428 had the lowest (2.8%). Gene expression analyses revealed significant drought-induced variation across cultivars and time points. Transcript levels were notably higher in drought-tolerant cultivars, particularly at 14 DPTI and 24 h post-rewatering, aligning with the morpho-physiological screening results. However, gene expression declined as the drought severity increased. These results suggest that California Blackeye, TVu11987, Lobia-I-Sefade, K929, and Aloomba were more drought tolerant compared to Mississippi Silver and TVu2428. Future research using transcriptomic profiling could unravel the complex molecular mechanisms of drought responses in cowpeas, providing valuable insights for breeding genotypes with improved resiliency to drought.