The Biocontrol Strain Bacillus subtilis Z-294 Alleviates Pepper Phytophthora capsici Disease Associated with Microbial Community Structure

The soil-borne oomycete pathogen Phytophthora capsici poses a serious threat to plant growth and results in substantial economic impact on the pepper industry. Therefore, the isolation of multifunctional biocontrol agents has become a major research priority. In this study, we isolated a biocontrol strain, Bacillus subtilis Z-294, which demonstrated strong inhibition of P. capsici in both plate and greenhouse experiments. This strain Z-294 exhibited broad-spectrum antagonistic activities as well as plant growth-promoting ability. Phylogenetic analysis based on core-genome and average nucleotide identity (ANI) further identified Z-294 as B. subtilis. Importantly, we found that the strain Z-294 alleviates the P. capsici disease through mechanisms associated with changes in the plant microbiome. Plants treated with Z-294 showed higher alpha-diversity. The application of B. subtilis Z-294 showed that the relative abundance of Alphaproteobacteria, Bacilli, Bacteroidia, Agaricomycetes, and Eurotiomycetes increased, while the relative abundance of Gammaproteobacteria and Sordariomycetes declined. Strain Z-294 holds great promise as a multifunctional biocontrol agent for the sustainable management of diseases and the enhancement of plant health, laying a solid foundation for its future agricultural applications.