Cluster bagging modifies flavonoid profiles in teinturier grape Garnacha Tintorera: Tissue-specific responses under different cultivation environments.

Light plays a crucial role in grape berry ripening and flavor compounds metabolism. Garnacha Tintorera, a teinturier grape cultivar, accumulates flavonoids in both skin and pulp, exhibiting distinct tissue-specific characteristics. To investigate light effects on flavonoid accumulation across different tissues and growing environments, a three-year (2018-2020) cluster bagging experiment was conducted from pre-veraison to harvest in the open-field vineyard and greenhouse. Bagging significantly reduced anthocyanins and flavonol accumulation in the skin, while no consistent response pattern was observed in the pulp, and flavanol accumulation was only marginally affected. Cluster bagging reduced the proportion of F3'5'H-derived anthocyanins across all tissues. Flavonols showed a consistent result only in the pulp, whereas flavanols exhibited an opposing but relatively weak trend. Light-responsive biomarkers in the skin varied between cultivation environments, whereas pulp biomarkers remained consistent. The study revealed tissue-specific flavonoid responses to light exclusion, providing insights for optimizing teinturier grape cultivation.