Objective To analyze the disease prevention mechanisms of endophytic bacteria against Colletotrichum siamense causing Camellia oleifera anthracnose.

Method Identification of endophytic bacterial strain B11 was based on morphological traits and multigene fragment-based phylogenetic analysis. The inhibitory effect of strain B11 on C. siamense was evaluated using the dual-culture method. The disease-suppressing and induced resistance mechanisms of the endophytic bacteria were investigated through scanning electron microscopy, amplification of compound synthesis genes and RT-qPCR.

Result The endophytic bacterial strain B11 was identified as Bacillus halotolerans. This strain exhibited broad-spectrum in vitro antimicrobial activity, with significant inhibitory effects on C. siamense. Its fermentation broth caused disruption of the cell wall of C. siamense strain CA17, leakage of intracellular contents and abnormal swelling of hyphae. Additionally, after treatment with the fermentation broth of strain B11, the marker genes PR1 and PR5 in the salicylic acid (SA) signaling pathway were upregulated in Arabidopsis thaliana leaves. Following treatment with the fermentation broth, the activities of defense-related enzymes POD and SOD in Camellia oleifera leaves significantly increased.

Conclusion This study provides important theoretical support for the research and development of green prevention and control technologies for C. siamense, as well as the development and application of biological control agents.