Transcriptome Analysis of Pre-Storage 1-MCP and High CO2-Treated 'Madoka' Peach Fruit Explains the Reduction in Chilling Injury and Improvement of Storage Period by Delaying Ripening.

Cold storage of peach fruit at low temperatures may induce chilling injury (CI). Pre-storage 1-MCP and high CO2 treatments were reported among the methods to ameliorate CI and reduce softening of peach fruit. However, molecular data indicating the changes associated with pre-storage 1-MCP and high CO2 treatments during cold storage of peach fruit are insufficient. In this study, a comparative analysis of the difference in gene expression and physico-chemical properties of fruit at commercial harvest vs. stored fruit for 12 days at 0 °C (cold-stored (CS), pre-storage 1-MCP+CS, and pre-storage high CO2+CS) were used to evaluate the variation among treatments. Several genes were differentially expressed in 1-MCP+CS- and CO2+CS-treated fruits as compared to CS. Moreover, the physico-chemical and sensory data indicated that 1-MCP+CS and CO2+CS suppressed CI and delayed ripening than the CS, which could lead to a longer storage period. We also identified the list of genes that were expressed commonly and exclusively in the fruit treated by 1-MCP+CS and CO2+CS and compared them to the fruit quality parameters. An attempt was also made to identify and categorize genes related to softening, physiological changes, and other ripening-related changes. Furthermore, the transcript levels of 12 selected representative genes from the differentially expressed genes (DEGs) in the transcriptome analysis were confirmed via quantitative real-time PCR (qRT-PCR). These results add information on the molecular mechanisms of the pre-storage treatments during cold storage of peach fruit. Understanding the genetic response of susceptible cultivars such as 'Madoka' to CI-reducing pre-storage treatments would help breeders release CI-resistant cultivars and could help postharvest technologists to develop more CI-reducing technologies.