Evaluation of the Inhibitory Effects of Wuyiencin, a Secondary Metabolite of Streptomyces albulus CK-15, Against Sclerotinia sclerotiorum In Vitro.

Sclerotinia sclerotiorum (Lib.) de Bary, a destructive fungal pathogen with an extensive host range, causes various diseases with the potential to cause huge economic losses to crops worldwide. Streptomyces species produce secondary metabolites with variable structures and biological activities that offer possible control methods for crop diseases. Herein, we evaluated the inhibitory effects of wuyiencin, a secondary metabolite of Streptomyces albulus CK-15, against S. sclerotiorum. The results showed that wuyiencin markedly inhibited mycelial growth and germination and the formation of sclerotia. It also increased cell membrane permeability, resulting in leakage of intracellular substances in pathogen mycelia. Wuyiencin markedly decreased oxalic acid content and the activities of polygalacturonase and pectin methyl-galacturonic enzymes. Moreover, it downregulated Nox1, ITL, pph1, Caf1, and sca1, all genes related to growth and infection. Lesions were smaller and less pronounced on soybean (Glycine max [L.] Merr.) leaves pretreated with wuyiencin in vitro, and the inhibition rate reached 78.36%. The results suggest that wuyiencin holds promise for the management of diseases caused by S. sclerotiorum, and the findings provide clues on the mechanism of action.