Short-Term High-CO₂ Treatment Modulates Phenylpropanoid Metabolism and Antioxidant Capacity in Blueberries During...

Maintaining the nutritional and functional quality of blueberries during cold storage remains a postharvest challenge. This study evaluated the effects of short-term high-CO₂ treatments on phenylpropanoid-related metabolism in two commercially important blueberry cultivar-season combinations: Duke (Vaccinium corymbosum L., highbush; early-season, June harvest) and Ochlockonee (V. virgatum Aiton, rabbiteye; late-season, September harvest). Fruits were exposed to 15% or 20% CO₂ for 3 days at 1 °C and subsequently stored for up to 29 days at 1 °C. Phenolic compounds, antioxidant capacity, and the expression of selected phenylpropanoid-related genes, including flavonoid biosynthetic enzymes and R2R3-MYB transcription factors, were analyzed. Short-term CO₂ treatments were associated with transient transcriptional responses, particularly in anthocyanin-related pathways, together with genotype-associated differences in phenolic composition and antioxidant capacity during storage. Overall, the results indicate associations between CO₂ exposure and secondary metabolism under cold storage conditions and should be interpreted as correlative rather than mechanistic evidence of priming.