Bacillus velezensis HAB-2 enhances rubber tree seedling growth and induces resistance to foliar diseases

Powdery mildew and anthracnose severely limit latex production and cause economic losses, while current management relies mainly on synthetic fungicides which pose challenges to sustainable agriculture. This study investigated the dual effects of Bacillus velezensis HAB-2 rhizosphere inoculation on the performance of rubber tree seedlings and the properties of their rhizosphere soil. Field trials demonstrated that HAB-2 application significantly reduced powdery mildew incidence by 53.92% and anthracnose severity by 36.5%. Additionally, HAB-2 promoted the growth of rubber tree seedlings in both controlled and field environments, with the most pronounced increase observed in root fresh weight— 66.67% and 183.41%, respectively. Further analysis revealed that HAB-2 significantly enhanced the activity of defence enzymes and induced the upregulation of defence-related genes at multiple time points. Measurements of rhizosphere soil properties showed increased acid phosphatase activity and elevated levels of available phosphorus following HAB-2 application. Amplicon sequencing suggested that HAB-2 modulated the soil microbial community, promoting the enrichment of Sphingomonas , Paraburkholderia and Trichoderma . PICRUSt2 indicated changes in predicted microbial functions linked to plant health. Overall, this study demonstrates that B. velezensis HAB-2 promotes rubber seedling growth and enhances foliar disease resistance by inducing systemic resistance and reshaping the rhizosphere microbiome, offering a promising strategy for sustainable rubber tree cultivation.