Research PaperEffects of chlorine dioxide fumigation on redox balancing potential of antioxidative ascorbate-glutathione cycle in 'Daw' longan fruit during storage

- ClO2 fumigation can maintain ASA, GSH and NADPH redox balances in longan.
- ClO2 fumigation can enhance ASA-GSH cycle enzymes activities in longan.
- ClO2 fumigation can enhance NADPH regenerating enzymes activities in longan.
- ClO2 fumigation affects redox status to reduce H2O2 and longan senescence.

Redox status in ascorbate-glutathione (ASA-GSH) cycle plays a pivotal role in plant responses to physiological and environmental changes. The change of ASA-GSH redox potential is associate with oxidative stress leading to plant senescence. The present study was aimed to investigate the effects of gaseous ClO2 on the redox status involved in delaying fruit senescence during storage of harvested longan fruit (Dimocarpus longan Lour. cv. Daw). Fresh longan fruit were fumigated with 10 mg/L ClO2 for 10 min, packed into cardboard boxes and stored at room temperature for 7 d. The results show that redox status of the fruit determined by ASA/DHA, GSH/GSSG and NADPH/NADP ratios decreased steadily in ClO2 untreated control group during storage. On the contrary, those ratios increased immediately after ClO2 treatment before declining steadily afterwards. The activities of NADPH-generating dehydrogenases including glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase, and ASA-GSH cycle enzymes including ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase and glutathione reductase were upregulated upon the ClO2 treatment and remained stable for a few days. ClO2 treatment decreased hydrogen peroxide content and fruit senescence index, including browning and disease symptoms in pericarp during storage. It was concluded that the imbalance of redox status of ASA-GSH cascade involved senescence in 'Daw' longan, and ClO2 could maintain the redox balance, leading to the alleviation and delay fruit senescence.