Development and Evaluation of Powdered Formulations of Bacillus velezensis MSU01 for Biocontrol of Tomato Bacterial Wilt

Tomato (Lycopersicon esculentum Mill.) production is severely affected by bacterial wilt, a destructive disease caused by Ralstonia solanacearum, which poses a significant challenge to growers worldwide. This study aimed to develop powdered formulations of Bacillus velezensis MSU01 and evaluate their efficacy in controlling the disease and enhancing plant growth. Laboratory evaluation using the agar well diffusion assay demonstrated strong antagonistic activity of B. velezensis MSU01 against R. solanacearum, with an inhibition zone of 13.8 mm. Three powder formulations-talcum-based, corn starch-based, and kaolin-based were prepared and evaluated for physicochemical properties, bacterial viability during storage, seed germination, and disease control efficacy. All formulations showed excellent solubility and stable pH (7.03-8.67), with initial moisture contents ranging from 0.20%-2.17%. After 60 days of storage at room temperature, the kaolin-based formulation maintained the highest viable cell count (6.30 ± 0.30 log CFU/g), while the corn starch-based formulation showed the highest moisture content (5.24 ± 0.30%). The corn starch-based formulation most effectively reduced bacterial wilt, lowering disease incidence to 10.00 ± 0.00% and severity to 5.33 ± 4.16%, outperforming the chemical control (streptomycin). Seed germination rates were highest with the talcum-based formulation (96.67 ± 5.77%), comparable to the positive control and significantly greater than the negative control. Although shoot and root lengths did not differ significantly among treatments, all B. velezensis MSU01 formulations enhanced plant growth compared to the pathogen-only treatment. Overall, the corn starch-based formulation showed the greatest potential as a sustainable and efficient biocontrol agent for managing bacterial wilt in tomato.