Biocontrol of Crown Gall Disease of Cherry Trees by Bacillus velezensis

Crown gall disease (CGD), caused by <i>Agrobacterium tumefaciens</i>, is a common plant disease that leads to significant economic losses. Biological control is a sustainable and scalable method for managing CGD. In this study, we isolated three <i>Bacillus</i> strains from the rhizosphere soil of healthy cherry trees and investigated their biocontrol activities and the underlying mechanisms against CGD of cherry trees. The results demonstrate that the three <i>Bacillus</i> strains can effectively inhibit the growth of the pathogenic <i>A. tumefaciens</i> strain XYT58 in vitro under different culture conditions. The pot experiments showed that the three strains could prevent CGD in cherry seedlings. Using PCR amplification, we identified the genes responsible for the synthesis of difficidin, macrolactin, and bacilysin in the three strains. In addition, inoculation with strains WY66 and WY519 significantly enhanced the expression of JA, ET, and SA pathway-related genes in cherry plants. The presence of antibiotic synthesis-related genes in the <i>Bacillus</i> strains and the trigger of plant ISR may explain their ability to control CGD in cherry trees. The findings of this study provide a theoretical basis for the application and development of plant growth-promoting rhizobacteria <i>Bacillus</i> strains in the control of CGD.