Understanding Chilling Injury and Sugar Metabolism-Related Genes and Metabolites in 'Red Haven' Peaches.

Although cold storage is commonly used to extend peach fruit shelf-life, chilling injury (CI) can develop during low-temperature storage conditions and be expressed during exposure to ambient temperature. Therefore, the objectives of this study were to characterize and compare the differences in CI occurrence as well as sugar metabolism-related genes and metabolites in 'Red Haven' peaches stored at 0 °C and 5 °C, followed or not by storage for 3 days (d) at 20 °C (to simulate retail shelf conditions for the evaluation of CI incidence), together with fruit stored at 20 °C, and to identify significant associations between peach CI and sugar metabolism via multivariate analysis. Fruit collected at commercial maturity was stored at 0 °C, 5 °C, and 20 °C and assessed at harvest (0 d) and at 1, 3, 5, 15, and 30 d of storage, followed or not by storage for 3 d at 20 °C. Peaches kept for 30 d at 5 °C plus 3 d at 20 °C exhibited CI, expressed as decreased expressible juice. CI susceptibility was associated with reduced sucrose and increased glucose and fructose, while sorbitol contents were also lower in fruit stored at 5 °C, compared to those stored at 0 °C. This was paralleled by decreased expression of sucrose biosynthesis-related genes and by increased expression of sucrose and sorbitol breakdown-related genes as early as after 5 d of storage at 5 °C. Sugar metabolism changes that occurred during cold storage were maintained after exposure for 3 d to a temperature of 20 °C. The correlations between the evaluated features implied that alterations in sugar metabolism can modulate changes in CI susceptibility. These findings suggest that storage at 0 °C better preserves the sucrose homeostasis of 'Red Haven' peaches, reducing CI risk.