Dynamics of total phenolic content in different apple tissues and genotypes: impacts and relevance for breeding programs

• Total phenolic content in apples is regulated by tissue-specific genetic mechanisms.
• Phenolic content depends on the interaction of the genotypes and tissues at maturity.
• The overall trend of phenolics in apple tissues is independent of the genotype.
• Cultivar-specific dynamics is observed on the seasonal evolution of total phenolics.
• Different genotypes reflect on different tissue-specific regulation of polyphenols.

The content and quality of phenolic compounds in apple pulp, peel, and leaves constitute important nutraceutical properties of apples in the human diet and are equally important to plant ecology. Moreover, increased understanding of the dynamics of polyphenol synthesis in different apple tissues of different genotypes may assist in apple breeding programs. Thus, the present study aimed to analyze the levels of total phenolics in apple pulp, peel, and leaves from cultivars Aori27, Elstar, Fuji, and Mellow at harvest time. Significant differences in the total phenolic content were found between cultivars for all evaluated tissues, but the differences between cultivars were not consistent among tissues, indicating the potential existence of tissue-specific genetic regulation mechanisms, as well as cultivar-specific dynamics. Additionally, tissues of two cultivars, Fuji and Mellow, were analyzed in the last three months of fruit development, showing a similar overall evolution in the phenolic concentration for all tissues, but some notable cultivar-specific characteristics for apple pulp and peel. These results are relevant for apple breeding when we consider as selection criteria the nutraceutical properties of apple polyphenols, the speed and degree of pulp enzymatic browning, and the physiological and agro-ecological roles of polyphenols in different organs and tissues of apple trees.