In this study, antioxidant compounds (ascorbic acid; total phenolic, flavonoid and anthocyanin contents; and relative antioxidant capacity) and the profiles of sugars, organic acids, polyphenols and mineral composition were compared in the peel and pulp tissues of nine commercial peach cultivars. The antioxidant compounds, measured by a 96-well-microplate-reader, showed differences among cultivars. The phenolic profile determined by UPLC resulted in the quantification of hydroxycinnamates, flavonols (only in peel), flavanols and anthocyanins, which were differently distributed in both tissues. Peels contained the highest phytochemical composition, with the exception of sugars and organic acids. We found that the contents of flavonoids, anthocyanins and total phenolic compounds measured by spectrophotometry and UPLC-MS methodologies were highly correlated. The Spanish cultivar Calanda Tardio showed the highest antioxidant and sorbitol contents. Venus had the highest contents of ascorbic and citric acids, and Big Top had the highest sucrose content.

Brown rot, caused by Monilinia spp., provokes pre- and post-harvest damage in peach (Prunus persica (L.) Batsch), which causes an economic impact in the industry. With a view to breeding for increased tolerance to this disease, a screening test based upon artificial fruit inoculation was validated on several parental lines of a peach breeding program during the two-period harvest. In addition, cultivars with different total phenolic contents were included in the two-year study. All physicochemical fruit traits recorded at harvest showed differences among all cultivars. The antioxidant compound content determined using spectrophotometry (to measure ascorbic acid and antioxidant capacity) and UPLC-MS (to measure and identify phenolic compounds) also revealed important differences among all genotypes. The rate of brown rot lesion following fruit inoculation varied widely among cultivars, and it was possible to discriminate between highly and less susceptible cultivars. Cultivars with minimal development of damage were identified as germplasm with the desirable allele combination to increase brown rot tolerance in peach breeding programs. Finally, Pearson’s correlation coefficients (r) between pairs of variables were calculated, searching for any biochemical candidate conferring tolerance. The correlation of phytopathological traits with the antioxidant composition, concerning contents of ascorbic, neochlorogenic, and chlorogenic acids and total polyphenols in fruit, is discussed.