Development of oil-in-water emulsion formulation of Clavibacter michiganensis subsp. michiganensis specific bacteriophage and biocontrol efficacy

Abstract Bacterial wilt and canker of tomato, caused by the Gram-positive pathogen Clavibacter michiganensis , pose a significant threat to tomato growers worldwide. Current control methods depend primarily on the use of copper-based products, raising concerns about resistance development, phytotoxicity and environmental pollution. In this study, an oil-in-water formulation of Cmm -specific Phages33 was developed using the Taguchi method, a statistical method that could provide an alternative to previously used methods. Taguchi’s signal–to-noise ratio and analysis of variance were applied to determine the effect of the factors. The signal-to-noise ratio showed that the optimal conditions for producing an effective formulation were the oil type corn oil, an emulsifier ratio (glycerol: Tween80) of 5:5 (v:v), a homogenization time of 20 min and a homogenization speed of 5000 rpm. A verification experiment was then carried out with the optimum conditions and in vitro efficacy on Cmm -DB3 was determined to be 80.7%. The storage stability of the formulation at 4 °C and room temperature was determined and the formulation stored at + 4 °C maintained its efficacy even after 12 months, while the efficacy of the formulation stored at room temperature decreased significantly. The efficacy of the formulation obtained was also demonstrated by in-planta experiments. In pot experiments, the biocontrol efficacy of emulsion formulation of Phage33 was found to be 79.47%. Both in vitro and in planta studies confirmed the protective effect of the formulation against bacterial wilt and canker caused by Cmm in tomato plants. Our results suggest that the Phage33 emulsion formulation is a promising alternative to copper-based chemicals for disease control. Future research should focus on large-scale production of the formulation and testing its efficacy in greenhouse and field conditions.