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

Sclerotinia sclerotiorum, 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 SsEFA6 in the process of pathogenicity of S. sclerotiorum. Knockout of SsEFA6 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, SsEFA6 deletion did result in a significant decrease in mutant virulence, indicative of its indispensability in virulence. Therefore, SsEFA6 plays an essential role in appressoria formation, sclerotia production, and fungal virulence in S. sclerotiorum.