1-Methylcyclopropylene and heat treatment alleviate chilling injury in purple sweet potato by regulating ROS homeostasis

Abstract

Postharvest purple sweet potato is vulnerable to chilling injury (CI) under low temperature storage. In this study, the effects of heat air treatment (HA, 45 °C, 3 h), 1-methylcyclopropene (1-MCP, 1.0 μL L–1, 24 h), and a combination of HA and 1-MCP on CI in purple sweet potato stored at 4 °C were investigated. The results showed that HA, 1-MCP, and HA combined with 1-MCP treatments, all significantly slowed down the increase in CI index, malondialdehyde (MDA) content, and electrolyte leakage of purple sweet potato than found in control, while the combination treatment was proved the most effective method for enhancing chilling tolerance in purple sweet potato. Based on transcriptome analysis, glutathione metabolism was activated with high gene expression of IbPMM, IbGMP, IbGME1, IbGME2, IbGGP, IbGaIDH, IbGCS, IbGS2, IbMDHAR, IbDHAR, IbGR, and IbAPX in the combined treatment of HA and 1-MCP. In addition, HA+1-MCP exhibited reduced hydrogen peroxide (H2O2) and superoxide radical (O2·−) content and high levels of ascorbic acid (AsA) and glutathione (GSH), as well as catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione reductase (GR) activities in purple sweet potato. In conclusion, HA+1-MCP can effectively reduce chilling injury in purple sweet potato by enhancing enzymatic and non-enzymatic antioxidative level to maintain reactive oxygen species homeostasis during cold storage.