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

Common beans (Phaseolus vulgaris L) are an important staple crop valued for their high protein content and dietary benefits. However, Fusarium wilt, caused by Fusarium solani, is responsible for up to an 84% yield loss in bean production. This study aimed to isolate and evaluate novel Pseudomonas fluorescens from Lake Bogoria as potential biocontrol agents against F. solani. 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 Pseudomonas fluorescens 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. In vivo 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 Pseudomonas fluorescens as an effective biocontrol agent against F. solani, with additional benefits for common bean growth and yield improvement.