Isolation and Characterization of Endophyte Bacillus velezensis KOF112 from Grapevine Shoot Xylem as Biological Control Agent for Fungal Diseases

As the use of chemical fungicides has raised environmental concerns, biological control agents have attracted interest as an alternative to chemical fungicides for plant-disease control. In this study, we attempted to explore biological control agents for three fungal phytopathogens causing downy mildew, gray mold, and ripe rot in grapevines, which are derived from shoot xylem of grapevines. KOF112, which was isolated from the Japanese indigenous wine grape Vitis sp. cv. Koshu, inhibited mycelial growth of Botrytis cinerea, Colletotrichum gloeosporioides, and Phytophthora infestans. The KOF112-inhibited mycelial tips were swollen or ruptured, suggesting that KOF112 produces antifungal substances. Analysis of the 16S rDNA sequence revealed that KOF112 is a strain of Bacillus velezensis. Comparative genome analysis indicated significant differences in the synthesis of non-ribosomal synthesized antimicrobial peptides and polyketides between KOF112 and the antagonistic B. velezensis FZB42. KOF112 showed biocontrol activities against gray mold caused by B. cinerea, anthracnose by C. gloeosporioides, and downy mildew by Plasmopara viticola. In the KOF112-P. viticola interaction, KOF112 inhibited zoospore release from P. viticola zoosporangia but not zoospore germination. In addition, KOF112 drastically upregulated the expression of genes encoding class IV chitinase and beta-1,3-glucanase in grape leaves, suggesting that KOF112 also works as a biotic elicitor in grapevine. Because it is considered that endophytic KOF112 can colonize well in and/or on grapevine, KOF112 may contribute to pest-management strategies in viticulture and potentially reduce the frequency of chemical fungicide application.

Automated summary

This study investigated the potential of biological control agent KOF112 derived from Japanese indigenous wine grape to inhibit three fungal phytopathogens in grapevines. Results showed that KOF112, identified as a strain of Bacillus velezensis, effectively controlled gray mold, anthracnose, and downy mildew through antifungal substance production and upregulation of defense-related genes in grape leaves. The findings suggest that KOF112 could be a promising alternative to chemical fungicides for sustainable pest management in viticulture.