Role of exogenous melatonin involved in phenolic metabolism of Zizyphus jujuba fruit.

To investigate the effects of exogenous melatonin (MLT) treatment on the quality of postharvest jujubes, fresh 'Lingwuchangzao', and 'Dongzao' jujubes (Zizyphus jujuba Mill) were dipped in MLT solution at the dose of 0, 50,100 and 200 μmol L for 20 min. Results showed the exogenous MLT application significantly delayed the color change and firmness decline, and maintained the content of total soluble solids and titratable acidity of both jujube cultivars, (p < 0.05). It was demonstrated that the endogenous MLT content was increased by exogenous MLT treatment. Furthermore, phenolic compounds level was enhanced by MLT application, companied by the upregulated expression of main genes involved in phenolic biosynthesis, including phenylalanine ammonia-lyase, cinnamate 4-hydroxylase, chalcone synthase, flavonoid 3β-hydroxylase, leucoanthocyanidin reductase, and anthocyanidin synthase. Given the evidence from the present study, it's proposed that the exogenous MLT approach is a promising approach for maintaining quality attributes and delaying the senescence of postharvest jujubes.