Abstract: In our previous study, we demonstrated that inoculation of orange peels with Actinomucor elegan could induce the accumulation of disease-resistant components, red in color. Here, the red pigments were collected and purified to evaluate their antifungal activity against Penicillium italicum and the possible mode of action was investigated. The results showed that at concentrations of 50–200 μg/mL, the red pigments exhibited strong antifungal activity in a dose-dependent manner as demonstrated by the ability to inhibit spore germination, germ tube elongation, mycelial growth and biomass accumulation. Furthermore, the red pigments altered cell wall structure and chitin distribution, and reduced the content of chitin in the cell wall. They destroyed cell membrane permeability and decreased ergosterol and total lipid contents in the cell membrane, thereby affecting the normal function of the cell membrane. Our results demonstrated that the red pigments can be used as a promising natural alternative to chemical fungicides for controlling postharvest diseases of citrus fruits.

Key words: disease-resistant components, antifungal activity, antifungal mechanism, cell membrane, cell wall