Tissue-Specific Anthocyanin and Polyphenol Content in Sweet Cherry (Prunus avium L.): Effects of Freezing and Association with MYB-Based Genetic Variability

Sweet cherry (Prunus avium L.) is a rich source of phenolic compounds, including anthocyanins and polyphenols, which contribute to fruit quality and nutritional value. However, their distribution across tissues (flesh and skin) and stability under different postharvest freezing treatments remain poorly understood. This study characterized the phenolic profiles of 14 sweet cherry genotypes in different tissues (whole fruit, flesh, and skin) and assessed the effects of freezing storage conditions on compound stability using high-performance liquid chromatography. Results revealed pronounced tissue-specific patterns: most phenolic compounds, particularly total anthocyanins, neochlorogenic acid, rutin, and chlorogenic acid, were more than twofold higher in the skin than in the flesh. Substantial genotype-dependent variability was observed, with certain cultivars exhibiting markedly higher phenolic concentrations. Immediate freezing in liquid nitrogen preserved significantly higher levels of phenolics compared to delayed freezing at −70 °C, where several compounds showed considerable degradation, especially in separated flesh samples. Anthocyanin content increased strongly with pigmentation intensity, with darker-coloured genotypes showing up to a 50-fold higher concentration than lighter-coloured types. Molecular analysis identified MYB-associated polymorphisms corresponding to differences in phenolic accumulation and fruit pigmentation. These findings demonstrate that genotype and tissue type are key determinants of phenolic composition, while immediate postharvest freezing is essential for preserving bioactive compounds. The combined biochemical and molecular approach provides novel insight into the regulation and stability of phenolic compounds in sweet cherry and supports the selection of cultivars with enhanced nutritional quality and improved postharvest performance.