Melatonin Maintains Fruit Quality and Reduces Anthracnose in Postharvest Papaya via Enhancement of Antioxidants and Inhibition of Pathogen Development

Abstract

Papaya fruit is widely grown in tropical regions because of its sweet taste, vibrant color, and the huge number of health benefits it provides. Melatonin is an essential hormone that governs many plants′ biological processes. In the current study, the impact of melatonin on fruit ripening and deterioration in postharvest papaya fruit was explored. An optimum melatonin dose (400 μmol L−1, 2 h) was found to be effective in delaying fruit softening and reducing anthracnose incidence. Melatonin enhanced antioxidant activity and decreased fruit oxidative injury by lowering superoxide anion, hydrogen peroxide, and malondialdehyde content by enhancing the enzymatic and non-enzymatic antioxidants, and by improving the antioxidant capacity of papaya fruit. Melatonin increased catalase, ascorbate peroxidase, NADH oxidase, glutathione reductase, polyphenol oxidase, superoxide dismutase, and peroxidase activity, as well as induced total phenol, total flavonoid, and ascorbic acid accumulation. Melatonin also enhanced the activity of defense-related enzymes, such as chitinase, 4-coumaric acid-CoA-ligase, and phenylalanine ammonia lyase, while it repressed lipid metabolism. Additionally, melatonin inhibited the development of anthracnose in vitro and in vivo. These findings suggest that exogenous melatonin application improves papaya fruit quality by boosting antioxidant and defense-related mechanisms.

Melatonin Treatment Maintains the Quality of Fresh-Cut Gastrodia elata under Low-Temperature Conditions by Regulating Reactive Oxygen Species Metabolism and Phenylpropanoid Pathway

“…Previous studies have revealed that exogenous MT can enhance the AsA-GSH cycle by increasing AsA content, thereby maintaining the quality of guava fruit and enhancing its disease resistance [ 36 ]. Treatment with MT has been shown to increase the AsA content in papaya fruit and improve its quality [ 37 ]. Aghdam et al demonstrated that the application of MT effectively improved the levels of AsA and GSH in pomegranate fruit [ 33 ].…”

Metabolic Profiling and Molecular Mechanisms Underlying Melatonin-Induced Secondary Metabolism of Postharvest Goji Berry (Lycium barbarum L.)

“…Our results coincided with the findings of Qu et al [25], who reported that MLT induced the activities and related genes of defenserelated enzymes (POD, PAL, C4H, 4CL, and CAD), thus strengthening disease tolerance in postharvest blueberry fruit. In postharvest plum fruit [37] and papaya [34], MLT-induced increase in POD, PAL, C4H, and 4CL activities was found to be associated with reduced anthracnose and retention of fruit quality. As reviewed by Li et al [33] and Arnao and Hernández-Ruiz [15], MLT treatment induces phenylpropanoid metabolism in the fruits by elevating the activities and expressions of phenylpropanoid pathway-related enzymes (e.g., PAL and POD), which in turn improves resistance against pathogens.…”

“…The current study showed that exogenous MLT treatment reduced disease incidence and lesion expansion in goji fruit during postharvest storage. As a potential antifungal agent, exogenous MLT has been shown to play positive roles in combating pathogens and restricting the postharvest decay in grapes [33], blueberry fruit [25], papaya [34], cherry tomato [35], and apple fruit [36]. Exogenous MLT application to postharvest fruit enhances the content of endogenous MLT, which, in turn, regulates many physiological changes in the fruit, including quality changes, senescence deterioration, and stress tolerance [20].…”

Insights into the Isolation, Identification, and Biological Characterization Analysis of and Novel Control Strategies for Diaporthe passiflorae in Postharvest Passion Fruit

“…In vitro inhibition experiments were carried out with slight modifications following the methods described by Fan et al [40]. The ε-PL, SA, and MT were added to the PDA medium to give final concentrations of 0.125, 0.25, and 0.5 mg/mL of ε-PL, 0.4, 0.8, 1.2, and 1.6 mg/mL of SA, and 1, 2, 4, and 8 mg/mL of MT.…”