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Characterization of the effect of HSAF from Lysobacter enzymogenes on Fusarium graminearum

Yangyang Zhao: Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences

<div><em>Fusarium graminearum</em> is a major pathogenic fungus that causes <em>Fusarium </em>head blight (FHB) disease on various cereal crops. Heat-stable antifungal factor (HSAF), which was found in <em>Lysobacter enzymogenes</em>, belongs to the polycyclic tetramate macrolactam family (PTM). HSAF was demonstrated to be a powerful antifungal agent showing activity against a number of plant pathogens, and effective in inhibiting <em>F. graminearum</em>. In this study, we investigated the effect of HSAF on the mycelia and conidia of <em>F. graminearum </em>PH-1. We determined that the effective concentration of HSAF to inhibit 50% mycelial growth of PH-1 was 4.1 μg/mL (EC<sub>50</sub> value). The production and germination of conidia were completely inhibited with 6 μg/mL and 1 μg/mL HSAF, respectively. Furthermore, we observed that different concentration of HSAF treatment led to morphology changes of hypha and conidia, such as the occurrence of wavy hyphae with increased branching, more germinating spots of conidia and swelling conidia. To further study the effect of HSAF on subcellular morphology of PH-1, we conducted TEM observation and found that 5 μg/mL HSAF could result in plasmolysis, invagination of plasmalemma and more lipid bodies. Further exploration on the mechanism of action of HSAF will provide clearer insight into its use as a fungicide to control FHB disease.</div>