Effects of the peptide H-OOWW-NH2 and its derived lipopeptide C12-OOWW-NH2 on controlling of citrus postharvest green mold

Abstract

The present study evaluated the antifungal properties of tetrapeptide H-OOWW-NH2 (O3TR) and its derivative lipopeptide C12-OOWW-NH2 (C12O3TR) against Penicillium digitatum, one of the main postharvest pathogens in citrus, and the possible mechanisms of their antifungal action. The results showed that the peptides O3TR and C12O3TR could inhibit conidial germination, induce conidia death and reduce the survival of mycelia of P. digitatum in vitro. The antifungal properties of O3TR and C12O3TR against P. digitatum were thermostable (40 °C–80 °C), insensitive to the change of pH (3–10) and varying sensitive to the presence of cations (Na+, Ca2+). In addition, the two peptides could effectively control green mold on citrus in vivo study. In terms of safety evaluation, the hemolytic activity of O3TR was neglectable, and significantly lower than that of C12O3TR, both of which were much lower than that of commercial prochloraz. The signals and intensity of fluorescent dye SYTOX Green (SG) and Propidium Iodide (PI) showed that O3TR and C12O3TR could enhance the mycelial and conidial membrane permeabilization. The antifungal action of O3TR and C12O3TR was further demonstrated by the release of cellular constituents and extracellular conductivity. In conclusion, the two peptides have a promising prospect to be applied as antifungal agents for the control of the green mold of citrus postharvest diseases.