Insights into Postharvest Pericarp Browning in Litchi

Litchi (Litchi chinensis Sonn.) is a high-value subtropical fruit. The shelf life of litchi fruit after harvest is largely limited during transportation and commercial circulation due to rapid pericarp browning, which drastically reduces consumer acceptability. Pericarp browning is a complex senescence process jointly modulated by internal genetic characteristics and external postharvest environmental factors. This review systematically summarizes multi-layered research advances in litchi pericarp browning, covering cultivar and fruit traits, storage environmental regulations (temperature, gas composition, relative humidity and water migration), browning reaction, energy homeostasis, hormone signal, multi-omics metabolic regulatory module, transcriptional factor network, and miRNA-mediated post-transcriptional regulation. The core roles of polyphenol oxidase, peroxidase and especially laccase in anthocyanin degradation and phenolic oxidation are highlighted, while the relationships among water, energy metabolism, membrane integrity and oxidative damage are discussed carefully. Currently, the priority research directions include to establish integrated water-redox-energy regulatory frameworks, construct multi-scale browning quantitative models, select browning-resistant varieties via genetic improvement, and develop safe and low-cost integrated postharvest handling to extend the shelf life and mitigate loss of postharvest litchi fruit.