Diversity of flesh polyphenols and their progressive dilution during fruit expansion in Malus germplasm

- Most variation in polyphenols derived from genetic diversity in Malus.
- Chlorogenic acid and procyanidin concentrations were diluted during fruit expansion.
- Fresh-cut browning was associated with both chlorogenic acid and procyanidin.

Fruit polyphenols are beneficial to human health as antioxidants, but high levels of these compounds diminish fruit appearance and flavor. In this study, we aimed to understand the variations in polyphenol variation and composition in Malus, including cultivars of the domesticated apple (Malus domestica). We quantified polyphenols in the flesh of ripening fruits from 20 Malus species (142 accessions), using high-performance liquid chromatography. We also analyzed dynamic changes in the levels of major polyphenols, procyanidin and chlorogenic acid, during fruit expansion. Total polyphenol concentrations (including chlorogenic acid and procyanidins) differed significantly across species and accessions, but intraspecific genetic diversity was the primary source of variation in polyphenol contents and compositions. We also found an effect of development. As fruit weight increased during fruit expansion, chlorogenic acid and procyanidin concentrations decreased continuously per unit fresh weight, but per-fruit concentrations either increased or remained constant. Finally, significant variability in fresh-cut browning positively correlated with chlorogenic acid and procyanidin concentrations, suggesting that these compounds can be targeted to decrease unfavorable apple appearance. In conclusion, the genetic diversity in M. domestica provides sufficient variation for the selection of future cultivars that are both visually appealing (less fresh-cut browning) and nutritious (higher levels of antioxidants).

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