The Guanine Exchange Factor SsEFA6 Participates in Appressorium Formation and Virulence in Sclerotinia sclerotiorum

<i>Sclerotinia sclerotiorum,</i> a soil-borne phytopathogenic fungus with a broad host range, often leads to severe disease and significant economic losses in agricultural production. The guanine exchange factor EFA6 of ADP-ribosylation factor 6 (ARF6) has been extensively studied in animals, but its function in fungi is seldom reported. Here, reverse genetics methods were employed to explore the effects of <i>SsEFA6</i> in the process of pathogenicity of <i>S. sclerotiorum</i>. Knockout of <i>SsEFA6</i> hindered appressoria formation and sclerotia production. However, it did not affect the secretion of oxalic acid, the sensitivity to cell wall inhibitors, or hyperosmotic stress. Nevertheless, <i>SsEFA6</i> deletion did result in a significant decrease in mutant virulence, indicative of its indispensability in virulence. Therefore, <i>SsEFA6</i> plays an essential role in appressoria formation, sclerotia production, and fungal virulence in <i>S. sclerotiorum</i>.