Abstract: To clarify the antifungal effect and mechanism of p-anisaldehyde against Geotrichum citri-aurantii, in vitro and in vivo experiments were conducted to identify the antifungal capacity of p-anisaldehyde. Moreover, the cell wall integrity, membrane permeability and fungal morphology of G. citri-aurantii were investigated to analyze the possible antifungal mechanism of p-anisaldehyde. Results showed that p-anisaldehyde could strongly inhibit the growth of G. citri-aurantii, and the minimum inhibitory concentration (MIC) value and minimum fungicidal concentration (MFC) value were both 4.48 g/L. Waxing with 10 MFC p-anisaldehyde could effectively delay the incidence of sour rot in citrus fruit, which was only 30% at 13 days after inoculation, significantly lower than the 100% incidence of the control (P < 0.05). Furthermore, p-anisaldehyde increased the activity of extracellular alkaline phosphatase (AKP), and damaged the cell wall integrity of G. citri-aurantii mycelia. Moreover, addition of sorbitol could not reverse the inhibition. Propidium iodide (PI) staining indicated that p-anisaldehyde could impair the cell membrane of G. citri-aurantii. Also, the hyphae treated with p-anisaldehyde appeared to be wrinkle, shriveled and distorted under scanning electron microscopy (SEM). It can be illustrated that p-anisaldehyde can effectively inhibit the growth of G. citri-aurantii and delay the progression of sour rot. In addition, the inhibitory mechanism of p-anisaldehyde is probably related to the damage caused by it to the cell wall and membrane of the mycelia.

Key words: p-anisaldehyde, Geotrichum citri-aurantii, antifungal ability, citrus fruit, antifungal mechanism