Inhibitory effect of ε-poly-L-lysine on fruit Colletotrichum gloeosporioides through regulating organic acid metabolism and exerting membrane-targeted antifungal activity

Abstract

Colletotrichum gloeosporioides (C. gloeosporioides) is the eighth harmful fungus among the top ten fungal pathogens in plant pathology, and the anthrax is a highly infectious disease caused by it. More efficient and environmental-friendly biological fungicide is needed to control anthrax. This study analyzed the inhibition mechanism of ε-poly-L-lysine (ε-PL) on C. gloeosporioides from the perspective of organic acid metabolism and membrane targeting. The results showed that ε-PL had a better inhibitory effect on C. gloeosporioides in vitro than commonly used chlorine source fungicides, such as chlorine dioxide and sodium hypochlorite. In vivo study, it was found that ε-PL reduced the expansion of anthracnose in winter jujube, fig, mango, tomato, apple and pitaya fruit. In addition, ε-PL had a remarkable impact on spore germination, germ tube elongation, mycelia morphology，and hypha density of C. gloeosporioides. From aspect of membrane targeting, ε-PL treatment destroyed the cell membrane of C. gloeosporioides, causing leakage of cell contents, lipid peroxidation of cell membrane and damage of mitochondria. In addition, from the results of pH and total acid determination, the pH of the control group decreased from 5.72 to 4.71, and the total acid content increased by 8.4 g L−1. High-Performance Liquid Chromatography (HPLC) results showed that C. gloeosporioides mainly producing malic acid, and its content accounted for 58.46% of the total organic acid, followed by citric acid, lactic acid and succinic acid. After 96 h of culture, the contents of four acids in 400 mg L−1 group were inhibited by 71.50%, 6.25%, 14.71% and 100% respectively, compared with the control group. The above results showed that ε-PL could play a remarkable antifungal role by causing membrane damage of C. gloeosporioides and regulating the organic acid metabolism.