Variation of Carotenoids and Polyphenolics in Peach (Prunus persica L.) and Implications on Breeding for Modified Phytochemical Profiles

Current medical research suggests that associations between generalized plant measurements of anti-oxidant capacity and recognized human biomarkers of disease or definitive health endpoints is inconsistent and often inconclusive. Detailed information of individual constituents of known phytochemical classes may be more informative than measurements of overall antioxidant capacity.         Firm ripe fruit of peach cultivars, 'China Pearl', 'Contender', 'Carolina Gold', and advanced breeding selections 'NC Yellow' and 'NC 97-48' were collected from established trees at 2 North Carolina locations in 2009 and 2010 and frozen in liquid nitrogen. Utilizing tandem extractions and analysis with UPLC and LCMS, 10 carotenoids and 24 phenolic compounds were quantified separately in the peel and flesh. Statistically significant differences were noted among peach cultivars and advanced selections for beta-carotene, cyanidin-3-glucoside, cyanidin-3-rutinoside, cholorogenic acid, quercetin-3- glucoside, and individual procyanidins.  Peel anthocyanin (ANC) concentration ranged from 183 mg/100 g dry weight in 'Contender’ to non-detectable levels in 'NC97-48' and 'NC Yellow'.  'China Pearl' and 'Carolina Gold' produced ANC levels approximately half of ‘Contender’ and it was hypothesized they represent the heterozygous state of an ANC allele(s) present in 'Contender' but absent in the advanced selections ‘NC Yellow’ and ‘NC97-48’. Examination of the pedigrees of these cultivars and advanced selections provides additional support for this hypothesis.   Chlorogenic acid concentration also fit a discreet pattern of accumulation but was not related to the accumulation of ANC. ‘China Pearl’, ‘NC 97-48’, and ‘NC Yellow’ contained the highest levels of cholorogenic acid (105-136 mg/100g), ‘Carolina Gold’ contained the lowest (52 mg/100), and ‘Contender’ represented an intermediate phenotype (70 mg/100g dwt).  

       Using analysis of variance (ANOVA) statistically significant genetic variation was found for almost all compounds identified.  Significant variation for location and year were detected, but they often tended to be compound specific. For cholorogenic acid, 27.7% of the phenotypic variance was explained by location (year = non-significant), while 40.4% of the phenotypic variation of ANC was explained by difference in genotypes. Analyzing fruit from the same environment over 2 years or from 2 locations in the same year would not have adequately accounted for the variation associated with environment.    Our data show that at least one bioactive compound of interest (ANC) in peach can be followed at least in part through genetics, and that environment may play a more substantial role in accumulation of bioactives than originally thought.