Postharvest MeJA maintains the shelf quality of kiwifruit after cold storage by regulating antioxidant capacity and activating the disease resistance

To gain a deeper understanding of the mechanism of MeJA-induced resistance to soft rot in kiwifruit, we explored the effects of postharvest MeJA on physiological, antioxidant capacity, disease resistance enzymes, and transcriptomic during the shelf life of kiwifruit after cold storage. The results showed that postharvest MeJA promoted the respiration rate, inhibited the ethylene release rate in the early shelf life, kept balance of reactive oxygen species, antioxidant content, and disease resistance enzymes, and reduced the decay rate caused by soft rot during shelf life after cold storage. The effect of postharvest MeJA alone was significantly better than combined with 1-MCP. We have identified 2724 co-expressed differentially expressed genes (DEGs) in MeJA3 vs CK3 and MeJA12 vs MeJA3. Postharvest MeJA regulates the expression of genes in plant hormones such as jasmonic acid, ethylene, and ABA biosynthesis and signal transduction. Meanwhile, postharvest MeJA maintains the glutathione-ascorbate (GSH-ASA) cycle by promoting the glutathione and ascorbic acid synthesis and inhibiting its decomposition and maintains phenolic content by upregulating the expression of PAL and C4H and inhibiting the expression of downstream genes in the phenylpropanoid pathway. Additionally, we also found that postharvest MeJA regulates disease resistance genes, including CNL, RLP, TNL, and NL domains. Transcription factors (TFs) such as SCL1, WRKY24, and TIFY10b may be involved in the regulation of disease resistance in kiwifruit by postharvest MeJA. The lesion diameter of kiwifruit inoculated with Botryospaeria dothidea significantly increased after 6 days of cold storage for 90 days, postharvest MeJA significantly increased the activities and gene expression of disease resistance enzymes and inhibited the increase of lesion diameter. In conclusion, postharvest MeJA maintains the shelf quality of kiwifruit after cold storage by improving antioxidant capacity and activating disease resistance.