Mulberry-derived endophytic Bacillus velezensis suppresses gray mold and promotes mulberry growth via reshaping the root metabolism and microbiome.

INTRODUCTION

Gray mold is an important fungal disease caused by Botrytis cinerea which threatens global agriculture. As chemical control faces limitations, biological control using Bacillus has gained attention for its environmental friendliness and growth promotion. However, their ecological basis and application potential in mulberry gray mold control remain insufficiently understood.

OBJECTIVE

This study aimed to evaluate the biocontrol efficacy of the mulberry derived endophytic strain Bacillus velezensis ZJU_268 and to investigate its associated effects on plant growth, root-associated microbiomes, and metabolic profiles.

METHODS

Greenhouse assays were combined with genomic and comparative genomic analyses, amplicon sequencing, non-targeted metabolomics, and functional validation of isolated microbes and metabolites to assess the effects of ZJU_268 and its cell free supernatant (CFS) on mulberry seedlings.

RESULTS

This study isolated a mulberry derived endophytic bacterium, B. velezensis ZJU_268, which exhibits strong antifungal activity and reduces the incidence of gray mold in mulberry seedlings. Whole-genome sequencing and comparative genomic analyses revealed strain-specific regions and genes associated with root colonization, stress adaptation, and antimicrobial biosynthesis. Both live cells and CFS significantly promoted seed germination, seedling growth, and biomass accumulation in a dose dependent manner. Amplicon sequencing showed that ZJU_268 and its supernatant reshaped the mulberry root microbiome, enriching beneficial bacterial and fungal taxa while reducing potentially pathogenic members. Cultivable members of the enriched microbiota displayed strong antifungal activity against B. cinerea and promoted mulberry growth. Metabolomic profiling further showed that ZJU_268 and its supernatant were associated with marked metabolic shifts in mulberry roots, accompanied by the accumulation of selected metabolites that supported the growth of representative enriched isolates.

CONCLUSIONS

This study demonstrates that ZJU_268 suppresses gray mold and promotes mulberry growth in association with direct antagonistic activity, microbiome restructuring, and holobiont-level metabolic shifts, providing a promising biological strategy for sustainable mulberry disease management.