Effects of selenium fertilization on fresh-cut browning in sweet potatoes and its mechanism analysis

Browning is a major factor affecting the quality of fresh-cut fruits and vegetables. As an essential component of glutathione peroxidase, selenium (Se) plays a crucial role in enhancing plant stress resistance and has shown potential in the postharvest preservation of horticultural products. To explore the effects and underlying mechanisms of Se fertilizer on postharvest browning in sweet potatoes, foliar Se was applied during the tuber expansion stage. Four treatments were established: a control group without Se application (CK) and three Se treatments at 30 (Se1), 60 (Se2), and 120 (Se3) g hm-2. Se application significantly delayed browning in fresh-cut sweet potatoes, with the inhibitory effect increasing alongside Se concentration. During storage, Se treatment effectively suppressed enzymatic browning by modulating key physiological and molecular pathways. Specifically, Se application reduced the activities of browning-related enzymes, including polyphenol oxidase (PPO), peroxidase (POD), and phenylalanine ammonia-lyase (PAL), while also lowering the accumulation of phenolic compounds. In addition, Se mitigated cutting-induced oxidative stress by reducing reactive oxygen species (ROS) production and membrane lipid peroxidation, thereby maintaining membrane integrity. The antioxidant defense system was enhanced, as evidenced by increased activities of superoxide dismutase (SOD) and catalase (CAT), which improved free radical scavenging capacity and preserved cellular redox homeostasis. At the molecular level, Se fertilizer downregulated the expression of genes involved in phenolic compound biosynthesis (IbPAL, Ib4CL, and IbC4H), phenolase enzymes (IbPPO and IbPOD), and lipoxygenase (IbLOX). This study provides a safe and effective strategy for controlling browning in fresh-cut fruits and vegetables, while also offering theoretical insights into the mechanisms by which Se modulates postharvest browning in sweet potatoes.