Epsilon-poly-l-lysine (ε-PL) exhibits antifungal activity in vivo and in vitro against Botrytis cinerea and mechanism involved

ε-Poly-l-lysine (ε-PL) is a non-toxic food preservative, but the antifungal effect of ε-PL against postharvest pathogenic fungi has rarely been reported. Grey mold caused by Botrytis cinerea is one of the main postharvest diseases on fruit and vegetables. The objective of this study was to investigate the antifungal activity of ε-PL against B. cinerea in vivo and in vitro, and elucidate the underlying mechanism involved. ε-PL treatment significantly inhibited the incidence of grey mold rot on cherry tomato, strawberry, grape, and green pepper caused by B. cinerea. Moreover, in vitro assay showed that ε-PL exerted strongly antifungal activity against mycelial growth, spore germination, and germ tube elongation of B. cinerea, with the increase of the concentration of ε-PL. Furthermore, significant leakages of intercellular electrolytes and protein suggested that ε-PL treatment increased the membrane permeability of B. cinerea. Malondialdehyde (MDA) content and Annexin V-FITC/propidium iodide (PI) double staining assay confirmed that ε-PL treatment induced membrane disruption of the test pathogen. Morphological alterations after ε-PL treatment revealed severe damage to B. cinerea mycelia, which resulted in distortion and shriveling of mycelial surface. The results indicated that ε-PL exerted antifungal activity by inducing the membrane damage of B. cinerea, and ε-PL treatment was a promising approach to controlling postharvest grey mold on fruit and vegetables.