Biocontrol Potential of Rhizosphere Bacteria Against Root Rot in Cowpea: Suppression of Mycelial Growth and Conidial Germination.

The cultivation of cowpea (), a vital vegetable crop, faces significant threats from spp.-induced root rot. In this study, three fungal pathogens ( HKFf, HKFi, and HKFo) were isolated from symptomatic cowpea plants, and we screened 90 rhizobacteria from healthy rhizospheres using six culture media. Among these pathogens, TSA-10E showed a notable suppression of HKFo (63.21%), HKFi (55.16%), and HKFf (50.93%). In addition, KB-6 inhibited the mycelial growth of HKFi and HKFo by 42.39% and 47.93%, respectively. Critically, cell-free filtrates from TSA-10E and KB-6 cultures reduced conidial germination in HKFo and HKFi, highlighting their role in disrupting the early infection stages. In greenhouse trials, TSA-10E and KB-6 reduced disease severity by 48.7% and 40.4%, respectively, with treated plants maintaining healthy growth while untreated controls succumbed to wilting. Broad-spectrum assays revealed that TSA-6E and TSA-10E were potent antagonists against both economic and grain crop pathogens. These findings underscore the potential of rhizobacteria as sustainable biocontrol agents for managing root rot disease caused by spp. in cowpea cultivation.