Near-freezing temperature alters ROS metabolism and gene transcription to enhance peach chilling tolerance and aroma quality.

The effect of near-freezing temperature (NFT, -1.1 °C ± 0.1 °C) on reducing chilling injury (CI) and flavor loss in peaches was systematically evaluated. NFT effectively suppressed the incidence of internal browning (IB) in peach flesh, enabling for the maintenance of a normal ripening process after cold storage. Concurrently, NFT significantly diminished the malondialdehyde (MDA) level and facilitated the accumulation of ascorbic acid (AsA) and glutathione (GSH). This was achieved by augmenting the activities of antioxidant enzyme and the transcript levels of key genes within the AsA-GSH cycle. Moreover, the transcript levels of polyphenol oxidases (PpPPO1/2) and peroxidases (PpPOD3/6) were found to be inhibited under NFT condition, in contrast to the induction of superoxide dismutases (PpSOD3/5). In terms of flavor-related compounds, the content of fatty acid-derived C6 derivatives, aliphatic esters, and lactones increased markedly in fruits stored at NFT compared to the 0 and 5 °C groups. In addition, NFT treatment dramatically induced the transcript levels of fatty acid desaturase 2 (PpFAD2), lipoxygenase 1 (PpLOX1), alcohol dehydrogenase 1 (PpADH1) and acyltransferase 1 (PpAAT1), which are involved in the fatty acid oxidation pathway. In conclusion, NFT enhanced the chilling tolerance of peaches and preserved their aroma quality by precisely regulating reactive oxygen species (ROS) metabolism and related gene expression. This research provides valuable insights into post-harvest storage techniques for maintaining the quality of peaches during cold storage.