Near-freezing temperature (NFT) storage alleviates chilling injury by enhancing antioxidant metabolism of postharvest guava (Psidium guajava L.)

The effects of near-freezing temperature (NFT) storage on chilling injury and antioxidant metabolism of postharvest guava were investigated in comparison with 6 °C and 10 °C storage. NFT storage showed significant inhibition effects on guava chilling injury occurrence, increment in cell membrane permeability and malondialdehyde accumulation, and contributed to compact and well-organized cell structure at the end of storage. Besides, remarkable enhancements in radical scavenging activities (DPPH, ABTS), ascorbic acid (ASA) and glutathione (GSH) contents, and activities of catalase (CAT), superoxide dismutases (SOD), peroxidase (POD) and the ASA-GSH cycle-related enzymes were observed in NFT group, leading to the elimination of excessive hydrogen peroxide (H2O2) and superoxide anion (O2−.). Further investigation of expression levels of genes related to the ASA-GSH cycle confirmed that NFT induced the transcriptions of PguAPX2, PguMDHAR1, PguMDHAR3, PguGR1 and PguGR2, and activated antioxidant related enzymes, alleviating cell membrane damage and cell disintegration during storage, thus inhibiting chilling injury of guava.