Regulatory effects of catechin treatment on postharvest mango quality and key gene expression

【Objective】Mangoes account for 52% of global tropical fruit production, occupying a significant position among tropical fruits. As climacteric fruits, mangoes exhibit a marked increase in respiratory metabolism after harvest, leading to rapid ripening and senescence. Moreover, mango harvesting season coincides with high temperatures and heavy rainfall. These climatic conditions not only complicate harvesting operations, but also increase the risk of fruit rot and softening during post-harvest storage and transportation, severely restricting the development of the mango industry. Consequently, extending post- harvest storage duration, preserving fruit quality, and prolonging shelf life have become critical challenges that demand urgent solutions in the mango industry. Extensive research indicates that exogenous catechin treatment positively influences the maintenance of post-harvest fruit quality, though its application in mango preservation remains unreported. This study investigated the effects of exogenous protocatechuic acid treatment on the quality, ripening, and senescence of post-harvest mango fruit, as well as corresponding relative gene expression levels. This study aimed to provide a theoretical foundation for the research and application of protocatechuic acid in post-harvest fruit preservation.【Meth-ods】This study used 80% ripe Taiwanese mangoes collected from Yucai Town, Tianya District, Sanya City, Hainan Province. F ollowing harvest, the fruit was promptly transported to the laboratory, where diseased and damaged specimens were discarded. We selected mangoes with uniform size and undamaged exteriors. A short section of the fruit stalk was retained, and the remainder was trimmed. The fruit was immersed in a 0.1% sodium hypochlorite solution and a 0.05% Shibaogong solution for 20 minutes, then air- dried. An equal quantity of mangoes was randomly divided into two groups: one group was treated with 4 g ·L-1 protocatechuic acid via immersion for 20 minutes; the other group was treated with distilled water as the control. Physiological indicators of mango, including firmness, skin color, and respiration rate, were monitored throughout storage. We determined the effects of protocatechuic acid treatment on the activities of post-harvest antioxidant and disease- resistant enzymes, as well as the expression levels of their related genes. The regulatory mechanisms of 4 g·L-1 protocatechuic acid treatment on mango ripening, senescence and nutritional quality were analysed.【Results】Compared with the control group, proanthocyanidin treatment extended the storage life of mangoes and delayed both the decline in firmness and the colour change. Additionally, proanthocyanidin treatment reduced ethylene release, delayed the peak of soluble solids content, and slowed the decrease in titratable acidity. Moreover, catechin treatment reduced respiratory rates, hydrogen peroxide (H2O2) content, malondialdehyde (MDA) content, and decreased superoxide anion (O2 •- ) production rates. Compared with the control group, proanthocyanidin treatment increased the activity of superoxide dismutase (SOD), peroxidase (POD), chitinase (CHI), β-1,3-glucanase (GLU), ascorbate peroxidase (APX), catalase (CAT), phenylalanine aminotransferase (PAL), and polyphenol oxidase (PPO), as well as the relative expression levels of their corresponding genes.【Conclusion】Research shows that proanthocyanidin treatment significantly reduces the ripening rate of post-harvest mangoes, preserves their nutritional quality, and delays fruit senescence by regulating enzyme activity and the relative expression levels of related genes.