Cold shock treatment alleviates chilling injury in papaya fruit during storage by improving antioxidant capacity and related gene expression

Abstract

Low temperatures cause chilling injuries in post-harvest papaya fruit. It is important to understand and ultimately alleviate fruit chilling damages to mitigate the post-harvest loss. This work aimed at investigating the effects of cold shock treatment (CST) on chilling injury (CI), antioxidant capacity and related gene expression of papaya fruits. Papaya fruit cultivar ‘SunUp’ was treated with ice water (4 °C) for 1 h, and control fruit was remain un-treated. They were then stored at 5 °C for 30 days and subsequently at 25 °C for additional three days. Results showed that CST significantly reduced the incidence of CI, ethylene production and respiratory rate in papaya fruit. CST also maintained higher content of ascorbic acid (Vc) and DPPH radical scavenging activity, and resulted in lower levels of cell membrane permeability, malondialdehyde (MDA), O2•− and H2O2. Furthermore, the enhanced enzymatic activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) were found, whereas the reduced activity of lipoxygenase (LOX) was observed in CST fruits. The gene expression analysis showed that CpSOD2, CpCAT1, CpAPX2, and CpGR2 were significantly up-regulated. In conclusion, CST could be an effective approach for the CI reduction and quality maintenance of papaya fruits during cold storage.