Segregation of chlorogenic acids and flavonol glycosides in interspecific (Vaccinium corymbosum x V. darrowii) diploid F2 blueberry population
Creators: name: Kim, Yurah
Publisher: name: No Publisher Supplied
Year: 2022

description: Blueberry (Vaccinium spp.), belonging to the family Ericaceae and subsection Cyanococcus, is one of the richest sources of antioxidant phytonutrients among fresh fruits and receives much attention for its phenolic compounds associated with human health-related benefits. Chlorogenic acids, as predominant blueberry phenolics together with anthocyanins, also likely account for a large proportion of antioxidant activity. Flavonols, as one of six major flavonoid subclasses, are usually found in plants bound to sugars as O-glycosides and are the most abundant and widely distributed in nature. They have important roles as developmental regulators and/or signaling molecules in plants and have been associated with the prevention of various oxidative diseases.The aim of this thesis is to investigate the variation of phenolic compound and organic acid content in two divergent blueberry species, Vaccinium corymbosum and V. darrowii, and their F1 hybrids, and to evaluate segregation in the interspecific (V. corymbosum x V. darrowii) diploid blueberry F2 population for chlorogenic acid and flavonol glycoside phenotypic traits. The objectives of this thesis were to: (1) identify and quantify phenolic compounds and organic acids in blueberry using high-performance liquid chromatography, (2) evaluate the chlorogenic acid and flavonol glycoside profiles among six blueberry genotypes, (3) analyze the segregation pattern of phenolic phenotypes in a biparental F2 population derived from a cross between V. corymbosum and V. darrowii, and (4) classify the F2 individuals according to their relative composition of chlorogenic acids and flavonol glycosides.The thesis will first focus on the analysis of different phenolic compounds and organic acids in clones of two blueberry species. Four phenolic acids and ten flavonol glycosides were identified using LC-MS-MS, while three organic acids were identified using HPLC. Genotype significantly affects the variation of average concentrations and profiles of phenolic compounds in blueberry species. V. corymbosum fruits presented mainly acetyl-caffeoylquinic acids in their phenolic acid composition, while V. darrowii fruits exhibited higher levels of 3-caffeoylquinic acid, and the interspecific F1 hybrid fruits showed intermediate levels of both compounds. Except for V. corymbosum, in which syringetin was present in the highest quantity, quercetin occurred as the most abundant aglycone. Galactosides and glucosides were the most abundant conjugate sugars in V. corymbosum and V. darrowii blueberries, whereas rhamnosides and galactosides were the most abundant conjugate sugars in F1 hybrid fruits. It was also found that genotype significantly affects the level of organic acids in blueberry species. Citric acid was present in low quantities in V. darrowii, while quinic acid was present in low quantities in V. corymbosum, and both were present in intermediate levels in the F1 hybrids. These observations suggest that both phenolic compound and organic acid biosynthesis are regulated differently in species. Phenolic compounds in the segregating diploid F2 population showed largely continuous distribution for each compound value. All compounds segregated and most were approximately normally distributed, with one acetyl-caffeoylquinic acid isomer and syringetin-3-galactoside bimodally distributed. Many phenolic compounds also exhibited transgressive segregation. Gene models of blueberry phenolic compounds were determined in the F2 population using chi-square goodness of fit tests. For the studied compounds, results were found statistically non-significant, where the null hypothesis was Mendelian distribution in a single locus model. A principal component analysis showed that F2 individuals can be distinguished based on their phenolic compound profile. These findings suggest that most of the phenolic compounds examined in this study are quantitative in nature, likely involving multiple loci, and might be controlled by a single dominant gene.