Phenylalanine enhances the efficiency of sodium dehydroacetate to control citrus fruit decay by stimulating reactive oxygen metabolism and phenylpropanoid pathway

Postharvest citrus fruit are susceptible to decay and quality deterioration during storage. In this study, the addition of phenylalanine (Phe) to sodium dehydroacetate (SD) treatment on citrus fruit decay was investigated. Results showed that the addition of 1 g L- 1 Phe significantly improved the controlling efficiency of SD to citrus green mold incidence and natural rot diseases, which displayed a comparable level to that of imazalil and effectively maintained the fruit quality parameters including weight loss, titratable acid, vitamin C, and firmness. Meanwhile, addition of Phe could drastically reduce the contents of hydrogen peroxide, superoxide anion, and malondialdehyde by increasing the activities of catalase, superoxide dismutase, peroxidase, glutathione reductase, dehydroascorbate reductase, monodehydroascorbate reductase, ascorbate peroxidase and the levels of glutathione and ascorbic acid. It could also improve the activities of phenylalanine ammonia-lyase, cinnamate-4hydroxylase and 4-coumarate coenzyme A ligase and the phenolic and flavonoid levels. These results suggested that Phe could improve the controlling efficiency of SD to citrus fruit decay through stimulation of reactive oxygen species (ROS) metabolism and phenylpropanoid pathway.