Identification and validating native biocontrol bacteria Bacillus strain MZ3-12 against bacterial wilt

Tobacco bacterial wilt is a major threat to sustainable tobacco agriculture. To identify native biocontrol agents for managing this disease, this study integrated rhizosphere microbiome profiling with functional screening. Comparative 16S rDNA amplicon sequencing showed that disease-affected soils had higher abundances of pathogen-linked genera, while healthy soils were enriched in beneficial microbes such as Bacillus and Streptomyces. Then, we isolated thirty potential bacteria from healthy rhizospheres soil, and investigated the effect of screening potential bacteria on R. solanacearum growth, siderophore secretion, protease activity, and cellulase activity. Among these bacteria, four potential biocontrol bacteria were screened, including three Bacillus MZ3-12, MZ4-13, MZ9-28, and a Glutamicibacter MZ8-15. These strains significantly inhibited R. solanacearum growth and secreted highly active proteases, cellulases, and siderophores. They also promoted tobacco growth, increased plant dry weight and fresh weight, and enhanced the expression levels of genes related to the salicylic acid, jasmonic acid, and ethylene pathways. Furthermore, MZ3-12 displays considerable control effect on tobacco bacterial wilt in greenhouse and field conditions. Our results confirm that combining microbiome analytics with culture-based screening is an effective way to identify environment-friendly biocontrol agents, highlighting the role of Bacillus MZ3-12 in maintaining rhizosphere health and managing tobacco bacterial wilt.