Research PaperVarietal differences in polyphenol contents, antioxidant activities and their correlations in table grape cultivars bred in Japan

- The polyphenol content and other fruit quality traits were assessed during ripening.
- Ninety days after full bloom was selected as the optimum sampling time.
- Repeatability for polyphenol content measurements was high at 0.80.
- The polyphenol content and antioxidant activity were highly positively correlated.

To enhance the knowledge of polyphenol content variability in table grape breeding, the polyphenol content and other fruit quality traits (berry weight, skin color, L* value, anthocyanin content, soluble solids content and titratable acidity) were assessed during the ripening process, and varietal differences in polyphenol contents and antioxidant activities among table grape cultivars bred in Japan were examined. Based on the ripening patterns of an array of individual fruit quality traits, 90 d after full bloom was selected as the optimum time to evaluate the polyphenol content because no remarkable developmental changes were occurring. An analysis of variance showed that genotypic variance was high in the polyphenol content in association with small or negligible variance levels associated with ripening times, genotype × ripening time interaction, among vines within genotype, and vine × ripening time interaction. The repeatability value of the polyphenol content was high, as were the correlation coefficients between the values for each year and the means of 3 years. The polyphenol content was greater in the black- and red-skinned cultivars than in white-skinned cultivars. A linear positive correlation was observed between the polyphenol content and antioxidant activity. Increased polyphenol contents in grape berries will enhance the economic value of newly released cultivars of fresh and processed grapes. In future table grape-breeding projects, colored cultivars should be considered as promising breeding stocks because of their high polyphenol contents.