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

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 mu L L-1. Results of in vivo tests demonstrated that wax + citral (1 x MFC) treatment did not effectively inhibit the growth of P. digitatum in Ponkan mandarin fruit, whereas wax + citral (10 x MFC) treatment significantly decreased the incidence of green mold after 6 days of storage at 25 +/- 2 degrees C. Wax + citral (10x 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. (C) 2013 Elsevier B.V. All rights reserved.