Abstract: Studies have found that sodium dehydroacetate (SD) can effectively inhibit the growth of Penicillium digitatum but its inhibitory mechanism remains unclear. In this study, the antifungal mechanism of SD was analyzed by measuring the effects of different concentrations of SD on the cell structure and function (cell wall, cell membrane and mitochondria) of P. digitatum mycelia. Results showed that SD entered the cells by active transport after 30 min of treatment and intracellular SD concentration was maintained at a high level during the treatment period. Compared with the untreated control group, the fluorescence intensity of cell wall and the extracellular alkaline phosphatase (AKP) activity of SD-treated mycelial cells were not significantly different, whereas propidium iodide staining showed that SD caused a significant increase in the fluorescence intensity of mycelia (P < 0.05), decreased the total lipid content of mycelia, and increased the extracellular pH, indicating that SD treatment directly damaged the cell membrane without damaging the cell wall. SD treatment also reduced the mycelial mitochondrial membrane potential and energy charge levels and increased Na+/K+-ATPase activity, thereby disturbing cellular energy metabolism. Intervention experiments showed that SD treatment effectively inhibited the incidence of green mold of inoculated kumquat fruit in a concentration-dependent manner. The above results indicated that SD exerts its antifungal effect and reduces the incidence of green mold in postharvest kumquat fruit by damaging the structure and function of the cell membrane and mitochondria of P. digitatum mycelia. These findings can provide a theoretical basis for the application of SD in the green control of postharvest kumquat diseases.

Key words: Penicillium digitatum; kumquat fruit; sodium dehydroacetate; antifungal mechanism; cell membrane; mitochondria