Abstract: To identify highly effective biocontrol resources for fruit-tree diseases, a strain of Bacillus velezensis, designated BVDT-1, was isolated and screened from residues generated during Cordyceps chanhua cultivation in Dongtou, Wenzhou, China. Its antagonistic activity against several fruit-tree pathogenic fungi was evaluated, and the potential molecular mechanisms underlying its biocontrol activity were investigated. In vitro dual-culture assays showed that strain BVDT-1 inhibited the mycelial growth of Pestalotiopsis microspora, Colletotrichum fructicola, and Fusarium equiseti by 81.98%, 74.22%, and 50.93%, respectively. A detached-twig biocontrol assay showed that the strain achieved a control efficacy of 32.40% against anthracnose of ‘Taishuu' sweet persimmon. Whole-genome sequencing and assembly of strain BVDT-1 were performed using a combination of Illumina HiSeq and PacBio sequencing technologies. The results showed that the genome of BVDT-1 consisted of a single chromosome of 3,916,789 bp with a GC content of 46.53% and contained 3,742 predicted open reading frames, 86 tRNA genes, and 27 rRNA genes. In addition, four genomic islands, three prophages, and four CRISPR-Cas systems were predicted. Functional annotation revealed that the genome of strain BVDT-1 harbored genes encoding fungal cell wall-degrading enzymes, such as chitinases, cellulases, and amylases, as well as 12 biosynthetic gene clusters associated with antimicrobial secondary metabolites, including surfactin, fengycin, and iturin. Three antibiotic resistance genes, vgbC, clbA, and vmlR, were also identified. In conclusion, strain BVDT-1 exhibited considerable antagonistic activity against fruit-tree pathogenic fungi and possessed abundant genetic resources associated with biocontrol. These findings indicate that BVDT-1 has promising potential for biocontrol applications and may provide a valuable microbial resource and theoretical basis for the development of biocontrol agents specifically targeting fungal diseases of fruit trees and for further elucidation of the underlying biocontrol mechanisms.

Key words: Bacillus velezensis, identification, biocontrol bacteria, whole-genome sequencing, Pestalotiopsis microspora, Colletotrichum fructicola, Fusarium equiseti