Antagonistic Effects of Bacillus Isolates against Botrytis cinerea Causing Tomato Gray Mold

Botrytis cinerea, the causal agent of gray mold, is a major fungal pathogen affecting tomato (Solanum lycopersicum) production worldwide. Due to increasing fungicide resistance and environmental concerns, alternative disease management strategies such as biological control have gained attention. In this study, we evaluated the biocontrol potential of four Bacillus isolates B. amyloliquefaciens PgBE1, PgBE14, PgBE51, and B. subtilis PgBE23 against B. cinerea. A dual culture assay revealed that all four bacterial isolates significantly inhibited mycelial growth of B. cinerea, with inhibition rates ranging from 67% to 73%. All isolates also exhibited cellulase, protease, and phosphate-solubilizing activities, suggesting their potential role in antagonism. Detached leaf assays showed that treatments with PgBE14, PgBE23, and PgBE51 substantially reduced lesion formation compared to the control. In whole-plant assays, these isolates decreased disease index and demonstrated biocontrol efficiencies comparable to the chemical fungicide Mirabit. These findings suggest that PgBE14, PgBE23, and PgBE51 are promising biological control agents for managing gray mold in tomato, warranting further investigation in field applications and formulation development.