Phyllosphere Bacillus subtilis Strain L-1 Enhances Resistance of Mango Leaves to Colletotrichum Infection

Mango (Mangifera indica L.), a major tropical fruit crop, suffers severe anthracnose damage caused by Colletotrichum spp., and traditional chemical control has environmental and food safety risks, with plant-microbe interaction-based biological control as a sustainable alternative. However, the regulatory role of phyllosphere microbiota in the tripartite interactions among mango, beneficial microbes and Colletotrichum remains unclear. This study explored phyllosphere microbiota's function in mango resistance to Colletotrichum and clarified the biocontrol mechanism of key beneficial isolates. We found Colletotrichum infection significantly reshaped mango leaf endophytic and epiphytic microbial communities, enriching Burkholderia, Acinetobacter, Bacillus and other dominant genera. We isolated a B. subtilis strain L-1 from the epiphytic microbiota that was 18-fold enriched in Colletotrichum-infected mango leaves. This strain exhibited potent antagonistic activity against Colletotrichum siamense with a relative inhibition rate of 82.10%, and delivered 79.77% biocontrol efficacy on mango leaves via two synergistic pathways: inhibiting pathogen spore germination and penetration by producing antimicrobial secreted metabolites and volatile organic compounds, and enhancing host disease resistance. Our findings advance the understanding of plant-phyllosphere microbiota-pathogen tripartite interactions and provide elite microbial resources for sustainable anthracnose management.