Effect of exogenous glucose and sucrose on quality maintenance of 'Huangguogan' fruit during postharvest storage

Citrus fruits are susceptible to postharvest quality deterioration. While exogenous sugar treatments have shown potential for modulating postharvest physiology, their mechanistic actions in citrus remain poorly defined. This study investigated the effects of exogenous sucrose and glucose on the postharvest quality of 'Huangguogan' fruit. Physiological analyses demonstrated that glucose reduced weight loss, while sucrose enhanced peel coloration and antioxidant capacity by reducing malondialdehyde accumulation. Notably, sucrose treatment (20 mM) induced metabolic shifts, elevating total soluble solids relative to controls. Sucrose treatment promoted sugar accumulation by coordinately upregulating biosynthetic enzymes (SPS, SS-synthesis) while suppressing catabolic activities (AI, NI, SS-cleavage), culminating in increased fructose and sucrose contents. Expression profiling revealed that sucrose treatment specifically activated the expression of multiple genes, including PAL1, P5CS1, and POD1, as well as SUS2, HXK2, and FRK1. The results demonstrate that exogenous sucrose maintains postharvest fruit quality through dual mechanisms of antioxidant system enhancement and sugar metabolic regulation.