Isolation and identification of a novel Bacillus velezensis strain JIN4 and its potential for biocontrol of kiwifruit bacterial canker caused by Pseudomonas syringae pv. actinidiae

Bacterial canker is a devastating disease in kiwifruit production, primarily caused by <i>Pseudomonas syringae</i> pv. <i>actinidiae</i>. In this study, a strain of <i>Bacillus velezensis</i> named JIN4, isolated from a kiwifruit branch, showed antagonistic activity. The <i>B</i>. <i>velezensis</i> JIN4 strain was identified based on its morphological, physiological and biochemical characteristics, 16S rDNA, and <i>gyrA</i> sequences. Furthermore, the complete genome of the strain was elucidated, revealing the presence of three genes that confer resistance to antibiotics, including tetracycline, lincomycin, and streptomycin. Additionally, a cluster of nine secondary metabolite synthesis genes was identified. In the laboratory, the JIN4 strain exhibited nitrogen (N) and phosphorus (P) production, demonstrating plant growth-promoting and broad-spectrum inhibitory activities against pathogenic fungi and bacteria. In the field, the JIN4 strain demonstrated effective colonization of kiwifruit, increased antioxidant enzyme activity, induced resistance in kiwifruit plants, and achieved a control efficiency of 60.22% against kiwifruit bacterial canker. These results indicate that <i>B</i>. <i>velezensis</i> JIN4 is a potential biocontrol agent against kiwifruit bacterial canker.