Characterization and Evaluation of Bacillus altitudinis WR7 as a Biocontrol Agent for Rubber Tree Anthracnose

Anthracnose, caused by Colletotrichum siamense, is a major limiting factor for global natural rubber production. To develop sustainable control strategies, seven bacterial strains with antagonistic activity against C. siamense were isolated from healthy rubber tree leaves, with strain WR7 demonstrating the most significant antifungal effect, exhibiting an inhibition rate of 82.36%. Pot experiments revealed that WR7 achieved a disease control efficacy of 71.65% against C. siamense-induced anthracnose. Genomic analysis identified WR7 as Bacillus altitudinis. This strain inhibits pathogen growth through multiple mechanisms, including disruption of the pathogen's cell wall and membrane integrity, induction of reactive oxygen species accumulation in hyphae, and secretion of cellulase, glucanase, protease, and siderophores. Gene cluster analysis further confirmed the potential of WR7 to synthesize antagonistic secondary metabolites such as lichenysin, fengycin, and bacilysin, while its sterile filtrate and volatile compounds also exhibited significant antifungal activity. Moreover, treatment with WR7 activated defense-related enzymes, including catalase and superoxide dismutase in rubber tree leaves, thereby enhancing the plant's defense responses. This study is the first to report that Bacillus altitudinis WR7 has potential as a biocontrol agent for managing rubber tree anthracnose, offering a novel resource for sustainable disease management in rubber production.