Ripening patterns (off-tree and on-tree) affect physiology, quality, and ascorbic acid metabolism of mango fruit (cv. Guifei)

The fleshy mango is a good source of l-Ascorbic acid (AsA) for humans. However, the effect of different ripening patterns (on-tree and off-tree) on mango fruit quality, AsA content, and AsA metabolism has not been studied. This study investigated the changes of ripening, quality, and AsA metabolism in ‘Guifei’ mangoes under different ripening patterns (off-tree and on-tree). Compared with off-tree, on-tree ripening significantly postponed peel coloration, preserved a high soluble solids (TSS) content, and suppressed ethylene biosynthesis of mango fruit. Malic acid gradually increased and replaced citric acid as the dominant organic acid in ripened fruit. Additionally, the activity of galactono-1,4-lactone dehydrogenase (GaILDH) decreased significantly as AsA content decreased, while enzyme activities and gene expressions of ascorbate oxidase (AO), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), and dehydroascorbate reductase (DHAR) increased during ripening process. Furthermore, correlation analysis revealed AsA content and GaILDH activity have a significant positive correlation, while there are significantly negative correlations between AsA and AO/APX activities, as well as their gene expression levels. Therefore, our findings suggested that on-tree ripening could delay fruit ripening, maintain high AsA content, and enhance mango fruit quality. This study has important theoretical and practical significance for mango production to optimize the harvest time and improve the fruit quality.