Green mold caused by Penicillium digitatum is the main postharvest disease in citrus fruits. The goal of this study is to evaluate the antifungal activity of chlorine dioxide (ClO2) against P. digitatum both in vivo and in vitro and to elucidate the underlying mechanism using flow cytometry and scanning electron microscopy. The results showed that 200-1800 mg/L of ClO2 significantly inhibited the incidence of green mold on kumquats, mandarins, Peru's oranges, and grapefruits caused by P. digitatum. Additionally, 200 mg/L of ClO2 significantly induced cell apoptosis of P. digitatum by increasing the fluorescence intensity of the mitochondrial membrane potential from 118 to 1225 and decreased the living cell rate from 96.8 to 6.1%. Further study demonstrated that the content of malondialdehyde and nucleic acid leakage (OD260) of P. digitatum markedly increased, and the mycelial morphology was seriously damaged with increased ClO2 concentration. These results indicated that ClO2 could inhibit fungal growth by destroying the membrane integrity of P. digitatum, and the use of ClO2 may be an alternative strategy to control green mold in postharvest citrus fruits.
Keywords: Penicillium digitatum; antifungal activity; chlorine dioxide; citrus fruit; fruit quality; membrane damage.