Pseudomonas fluorescens from Lake Bogoria, Kenya: a promising biocontrol agent against Fusarium solani in Phaseolus vulgaris L.

Common beans (<i>Phaseolus vulgaris</i> L) are an important staple crop valued for their high protein content and dietary benefits. However, Fusarium wilt, caused by <i>Fusarium solani</i>, is responsible for up to an 84% yield loss in bean production. This study aimed to isolate and evaluate novel <i>Pseudomonas fluorescens</i> from Lake Bogoria as potential biocontrol agents against <i>F. solani</i>. Using serial dilution, 30 bacterial isolates were obtained; 10 showed varied mycelial inhibition rates (5.95-42.86%) through dual culture and confrontation assays. Molecular identification using 16S rDNA confirmed that two isolates were <i>Pseudomonas fluorescens</i> strains. Antibiosis gene screening revealed the presence of 2,4-diacetylphloroglucinol, pyrrolnitrin, pyoluteorin and hydrogen cyanide. Enzyme assays demonstrated chitinase (1.33-3,160 U ml^-1) and chitosanase (12.67-29.00 mm) production, indicating antifungal capabilities. <i>In vivo</i> pot experiments with isolate TW17⁺ showed reduced wilt symptoms <20.0% and disease incidence (8.0-35.0%). These findings highlight the potential of soda lake-derived <i>Pseudomonas fluorescens</i> as an effective biocontrol agent against <i>F. solani</i>, with additional benefits for common bean growth and yield improvement.