Chlorine dioxide delays the reddening of postharvest green peppers by affecting the chlorophyll degradation and carotenoid synthesis pathways

The change in colour from green to red, known as reddening, is a major problem in green pepper cultivation, implying ripening and senescence. Chlorine dioxide (ClO2) is used to preserve the quality of vegetables and fruits because of its safety. In this work, the effects of ClO2 on reddening in green peppers, their chlorophyll and carotenoid content, and the molecular mechanisms involved are studied. The results show that 30 μL L−1 of ClO2 treatment reduced the reddening rate markedly compared to the control. ClO2 delayed the degradation of chlorophyll and significantly reduced the synthesis of capsanthin and β-carotene. Additionally, the transcript levels of pheophytin pheophorbide hydrolase (PPH), pheophorbide a oxygenase (PAO), and red chlorophyll catabolite reductase (RCCR) genes, associated with chlorophyll breakdown, were inhibited by ClO2 treatment, and the relative expression of phytoene synthase (Psy), lycopene β-cyclase enzyme (Lcyb), capsanthin/capsorubin synthase (Ccs), and β-carotene hydroxygenase enzyme (Crtz) genes, associated with carotenoid synthesis, were suppressed. These findings indicate that ClO2 delayed reddening by suppressing the expression of certain genes associated with chlorophyll breakdown and carotenoid synthesis in harvested green peppers.