Iturins produced by Bacillus velezensis Jt84 play a key role in the biocontrol of rice blast disease

Rice blast disease, caused by the plant pathogenic fungus Magnaporthe oryzae, severely constrains rice production worldwide. Using plant-associated microorganisms, biological control of rice blast is an efficient and environmentally friendly approach to disease management. Bacillus bacteria produce a broad array of antifungal lipopeptides, making them effective biological control agents. In a previous study, Bacillus velezensis strain Jt84 exhibited biocontrol activity against rice blast disease, and the antifungal compounds it produces were isolated by acid precipitation of cell-free supernatants extracted with methanol were lipopeptides. Lipopeptides showed a stronger inhibitory effect against M. oryzae and induced abnormal mycelial morphology. Further analysis using PCR and HPLC-ESI-MS confirmed the presence of surfactins, iturins, and fengycins. The results exhibited that iturins play an essential role in the antifungal activity against M. oryzae and confirmed these results through mutagenesis experiments used to suppress iturins biosynthesis. In conclusion, B. velezensis Jt84 significantly reduced the incidence of rice blast disease at the seedling stage, while B. velezensis Jt84ΔituB strain markedly reduced disease biocontrol effect, indicated that iturins produced by B. velezensis Jt84 strain play a key role in the biocontrol of rice blast disease.