Biological control of fusarium head blight in wheat using secondary metabolites of Bacillus subtilis BS-Z15

Fusarium head blight is one of the major diseases affecting wheat ears, and it is highly pathogenic and destructive. The pathogen, Fusarium culmorum, is a filamentous fungus capable of infecting crops, such as wheat, barley (Hordeum vulgare), and corn (Zea mays). The mycotoxins produced by this pathogen not only markedly reduce the nutritional value of grains but also pose a serious threat to public health. It has been shown that the antimicrobial substances in the secondary metabolites of Bacillus subtilis BS-Z15, mycosubtilin (Myco), and the crude extract of antimicrobial substances (AP), which contains the same content of Myco, can significantly inhibit the germination of conidia and mycelial growth of F. culmorum. It causes the spores to shrink and hyphae to break. The antimicrobial rate of A15 treatment reached roughly 77.77% after 4 days. Both AP and Myco reduced the disease index of wheat scab, with the control effect of AP reaching approximately 54.48% after 21 days of application. The control effect and inhibitory effect on pathogens of AP were superior to those of Myco at the same concentration. A transcriptome analysis indicated that the AP primarily regulates the proteasome pathway, DNA replication pathway, and peroxisome pathway in F. culmorum, while Myco primarily influences the proteasome pathway, fructose and mannose metabolism, and DNA replication pathway in this pathogen. Liquid chromatography-mass spectrometry was used to analyze the secondary metabolites of BS-Z15, and it was found that in addition to Myco, it also contains substances with antifungal activity or effects on plant growth, including 2-hydroxycinnamic acid, cinnamaldehyde, acrylamide, piperidine, myriocin, palmitic acid, L-histidine, and indole lactic acid. The secondary metabolites of BS-Z15 have demonstrated significant efficacy in the biological control of wheat scab by downregulating the expression of genes in pathways related to the conversion of compounds, energy metabolism, and cell growth of F. culmorum. The AP exhibits superior control and antimicrobial effects compared to Myco, which may be attributed to the synergistic interactions between Myco and other antimicrobial components found in the secondary metabolites of BS-Z15. This study provides a theoretical foundation for the further exploration of other antifungal components within the secondary metabolites of BS-Z15 and lays the groundwork to develop BS-Z15 as a biological control agent.