In vitro evaluation of rhizobacteria associated with diseased tomato plants for antagonistic activity against Ralstonia solanacearum, the causal agent of bacterial wilt

Bacterial wilt caused by the phytopathogen Ralstonia solanacearum is one of the most destructive diseases affecting the worldwide net production of tomato (Solanum lycopersicum L.). The present study aimed to isolate and determine the antagonistic effect of rhizobacteria associated with diseased tomato plants against the phytopathogen under in vitro conditions. A total of 32 bacterial strains were obtained from the rhizosphere of wilt-affected tomato plants and screened for their antagonistic activity using dual culture and agar well diffusion assays. Morphological, biochemical, and preliminary molecular characterizations were performed to identify the promising isolate. Among the isolates tested, a few exhibited significant inhibitory zones against R. solanacearum, indicating strong antagonistic potential. The isolate TRSAB1, later identified as Stenotrophomonas pavanii, showed potential in vitro growth inhibition of the phytopathogen as compared to the control. The result revealed that antagonist microbes associated with the rhizosphere soil of diseased tomato plants possess potential antagonist activities against the wilt pathogen and hence have prospects for exploration as a biocontrol agent. Further polyhouse and field evaluations are recommended to confirm their effectiveness and potential application in sustainable tomato disease management strategies.