Promising biocontrol potential of Bacillus velezensis P15 against Colletotrichum fructicola in tea plant

Anthracnose poses a serious threat to the yield and quality of tea plants, underscoring the urgent demand for effective biological alternatives to synthetic pesticides. This study characterized Bacillus velezensis P15, a strain with the highest antagonistic activities against seven distinct Colletotrichum species responsible for tea anthracnose compared with other tested biocontrol microbes. Remarkably, this bacterium inhibited at least 21 species of phytopathogens, and its biocontrol efficacy in vivo against anthracnose was comparable to or exceeded that of the fungicide thiophanate-methyl. Metabolites produced by B. velezensis P15 destroyed the mycelial morphology, altered the cell plasma membrane integrity, and disrupted the transcription response of Colletotrichum fructicola . Specifically, the expression of a series of genes involved in sterol and phospholipid biosynthesis as well as MAPK-mediated signaling pathways was suppressed, which is critical for the composition of the cell membrane and cell wall, fungal growth, stress adaptation and pathogenicity. Compared with the control, metabolites from B. velezensis P15 decreased the ergosterol content of C. fructicola by 91.72% while increasing its extracellular conductivity by 26.71%. The broad-spectrum antimicrobial activity, consistently high biocontrol performance on anthracnose, and multi-target mechanism of B. velezensis P15 position it as an efficient and safe biological control solution for tea anthracnose. • Bacllius velezensis P15 exhibited the strongest antagonism against 7 Colletotrichum spp. • Strain P15 inhibited at least 21 phytopathogens with broad-spectrum antimicrobial activity. • Efficacy of B. velezensis P15 against anthracnose matched or exceeded thiophanate-methyl. • P15 metabolites impaired membrane integrity and suppressed sterol, phospholipid, MAPK genes. • Strain P15 represents a promising and multi-target agent for sustainable tea disease control.