Inhibitory effects of glutaraldehyde on Geotrichum citri‐aurantii and its possible mechanism

AIMS: This study investigated the inhibitory effect of glutaraldehyde (GA) on sour rot in citrus fruit and the underlying antifungal mechanism on mycelial growth of the causative pathogen Geotrichum citri-aurantii. METHODS AND RESULTS: Glutaraldehyde exhibited a strong inhibitory effect on G. citri-aurantii, with a minimum inhibitory and fungicidal concentration (MFC) of 1·00 µl ml-1 . In addition, in vivo application of GA (1 × MFC and 5 × MFC) reduced the disease incidence of sour rot in citrus fruit by 60 and 80% respectively. Scanning electron microscopy results revealed that the morphology of G. citri-aurantii mycelia was greatly altered by GA treatment. Propidium iodide and Calcofluor White Staining revealed that the membrane permeability, rather than the cell wall integrity, of G. citri-aurantii mycelia was severely disrupted after the addition of GA. Massive accumulation of malonaldehyde and reactive oxygen species as well as an increase in lipoxygenase activity were observed. CONCLUSION: These results indicate that GA may inhibit the mycelia growth of G. citri-aurantii through a membrane damage mechanism induced by membrane peroxidation. SIGNIFICANCE AND IMPACT OF THE STUDY: Glutaraldehyde is expected to be a novel fungicide for controlling sour rot in citrus fruit.