Volatile Organic Compounds Produced by Bacillus velezensis GX0002980 Inhibit Colletotrichum fructicola : A GC-MS and Transcriptomic Analysis

One of the most significant diseases affecting mango production is anthracnose, which severely impacts yield and quality. In this study, Bacillus velezensis GX0002980, a strain isolated from the Guangxi Damingshan National Nature Reserve, and its volatile organic compounds (VOCs) exhibited strong antifungal activity against Colletotrichum fructicola, the causal agent of anthracnose. A total of 33 VOCs were identified by GC-MS. Antifungal assays using partitioned Petri dishes revealed seven VOCs with inhibitory activity, among which 2-ethylhexanol showed the greatest effect. Observations utilizing microscopy indicated that C. fructicola exposed to 2-ethylhexanol (2-EH) exhibited swollen, deformed, intertwined, and fractured hyphae with visible perforations. Fluorescent staining further confirmed that 2-EH disrupted the cell wall and cell membrane structure, while also inducing elevated mitochondrial reactive oxygen species (ROS) levels. RNA-seq analysis of C. fructicola exposed to 2-EH revealed multiple differentially expressed genes (DEGs) enriched in metabolic pathways related to the cell wall and membrane, as well as a significant downregulation of genes encoding key enzymes in the TCA cycle and energy metabolism. Collectively, our findings indicate that 2-EH inhibits C. fructicola by disrupting cell wall integrity, damaging the cell membrane and its permeability, suppressing energy metabolism, impairing the mitochondrial respiratory chain, and inducing ROS accumulation. Experiments conducted on harvested mango fruits indicated that 2-EH significantly delayed the development of anthracnose. Our study reveals that 2-EH effectively controls mango anthracnose. We further elucidate the underlying mechanism, showing that both B. velezensis GX0002980 and 2-EH directly inhibit C. fructicola.