Use of citral incorporated in postharvest wax of citrus fruit as a botanical fungicide against Penicillium digitatum

• Wax + citral treatment significantly reduced green mold in Ponkan fruit.
• Wax + citral treatment increased the Vc content and CAT, POS, SOD activities.
• Wax + citral treatment decreased the MDA content and PAL, PPO activities.
• Wax + citral treatment had minor effects on pH, CCI and TSS of tested fruit.

The antifungal activity of citral against Penicillium digitatum, the causal agent of citrus green mold, was tested by in vitro and in vivo experiments. In vitro assays showed that the minimum inhibitory concentration and the minimum fungicidal concentration (MFC) were both 4000 μL L−1. Results of in vivo tests demonstrated that wax + citral (1× MFC) treatment did not effectively inhibit the growth of P. digitatum in Ponkan mandarin fruit, whereas wax + citral (10× MFC) treatment significantly decreased the incidence of green mold after 6 days of storage at 25 ± 2 °C. Wax + citral (10× MFC) treatment remarkably increased the content of vitamin C and antioxidant enzyme activities such as catalase, superoxidase dismutase, and peroxidase but decreased the activities of phenylalanine ammonia lyase, polyphenol oxidase, and malonaldehyde. The treatment had minor effects on the pH, coloration index, and total soluble solids. This study provided theoretical data for the practical application of citral on citrus fruit quality during postharvest storage.