Melatonin treatment inhibits mango fruit (Cv. ‘Guiqi’) softening by maintaining cell wall and reactive oxygen metabolisms during cold storage

Abstract

Mango fruit (Mangifera indica L, cv. ‘Guiqi’) was treated with melatonin (1 mM) to explore the changing mechanisms in fruit softening and to examine the effects of melatonin on the interaction between the cell wall and reactive oxygen metabolisms subjected to cold storage. The results depicted that compared to control, melatonin treatment (1) improved storage life by maintaining the higher ascorbic acid (AsA) and reduced glutathione (GSH) contents, as well as maintained higher insoluble pectin, hemicellulose, and cellulose contents, and lower soluble pectin content of ‘Guiqi’ mango fruit. (2) Delayed fruit softening by maintaining higher firmness and suppressing the activities of polygalacturonase (PG), pectin methyl esterase (PME), cellulase (Cx), and β-glucosidase (β-glu); and cell wall degrading genes (MiPG14, MiPME, MiCel, and Miβ-glu). (3) Enhanced storage quality by inhibiting decay incidence, respiration rate, and weight loss rate; increased activity of glutathione reductase (GR) and inhibits reactive oxygen species (ROS) metabolites at cold storage. These results indicate that exogenous melatonin could delay mango fruit softening by maintaining cell wall metabolism, inhibiting ROS metabolites (O2.- and H2O2) accumulation via enhancement of non-enzymatic (AsA and GSH contents) and enzymatic (GR activity) antioxidants, and thus maintaining quality and improved storage life.