Abstract: This study was conducted to examine the antifungal activity of berberine hydrochloride (BH) on the growth of Penicillium digitatum and to elucidate the possible mechanism. The results showed that BH significantly inhibited the growth of mycelia with a minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of 0.16 g/L and 0.32 g/L, respectively. Meanwhile, the germination rate of spores was only (4.40 ± 1.05)% after 15 h of culture in the presence of BH at MIC, which was significantly lower than that recorded for the control group (92.48 ± 3.35)% (P < 0.05). BH at 10 MFC effectively delayed the development of green mold in postharvest citrus fruit. The lesion diameter was (1.13 ± 0.02) cm at five days after inoculation, which was significantly lower than that of the control group (5.62 ± 0.09) cm (P < 0.05). After BH treatment, the mycelia of P. digitatum were wrinkled and deformed as observed under a scanning electron microscope (SEM). Further experiments showed that the integrity of the mycelial cell wall and cell membrane was damaged after 30 min of BH treatment, accompanied by an increase in the activity of extracellular alkaline phosphatase and the content of soluble protein. However, the intracellular ATP content and energy charge levels decreased. After 60 min exposure, the accumulation of a large amount of reactive oxygen species (ROS) led to the peroxidation of membrane lipids, mitochondrial function damage and energy metabolism imbalance. In conclusion, BH can significantly inhibit the spore germination and the mycelial growth of P. digitatum and delay the progression of citrus green mold possibly by affecting cell permeability and energy metabolism.

Key words: berberine hydrochloride; Penicillium digitatum; citrus fruit; antifungal activity; antifungal mechanism