Shidong He，Dongliang Fang，Jinqi Wang，Liangshuai Fu，Junjie Liu，Yanbin Sun，Jinbiao Ma，Miao Zhou，Taotao Wang，Zheng Gao，Shuxin Zhang，Xiang Li 

Abstract

Fusarium solani is the primary pathogenic fungus causing postharvest Garlic Fusarium Rot (GFR), a disease that severely restricts the development of the garlic industry. This study confirmed that GFR not only induces browning and rot of garlic cloves, significantly reducing their commercial quality, but also poses a severe threat to food safety due to the toxic secondary metabolites produced by F. solani—specifically, neopatulin (with an 11.37-fold enrichment) and Monocillin I (with a 10.43-fold enrichment). To address this critical issue, we isolated and characterized a biocontrol strain (designated L271), which was identified as Bacillus velezensis. Both the strain and its cell-free supernatant (CFS) exhibit antifungal activity against a variety of pathogenic fungi, inhibiting the growth of 9 pathogenic fungal species in vitro. Specifically, strain L271 can effectively suppress the spore germination of F. solani and reduce the lesion diameter of GFR by 87.60 % in vivo. Additionally, the CFS of B. velezensis L271 significantly inhibits the growth of this pathogenic fungus. Fluorescence staining results showed that the CFS of B. velezensis L271 severely damages the cell membrane of F. solani and induces an intracellular reactive oxygen species (ROS) burst. In-depth analysis of the CFS components of B. velezensis L271 revealed that both its secreted proteins (SPs) and metabolites possess antifungal activity. Through liquid chromatography-mass spectrometry (LC-MS), gas chromatography × gas chromatography-time-of-flight mass spectrometry (GC×GC-TOF-MS) metabolomic analysis, and combined with metabolite antagonism experiments, 4-Hydroxybenzonitrile, 2,3-Dihydroxybenzoic acid, and 2-decanol were identified as the main antifungal substances produced by B. velezensis L271. These results suggest that B. velezensis L271 may have the potential to control postharvest garlic diseases. This study indicates that B. velezensis L271 is promising as a new biological agent for controlling F. solani in garlic and may help enhance our understanding of the biocontrol mechanisms of Bacillus strains.

Paper Linkage:https://doi.org/10.1016/j.postharvbio.2025.114143