POLYPHENOL VARIABILITY IN THE FRUITS AND JUICES OF A CIDER APPLE PROGENY

BACKGROUND: Polyphenols have a favorable antioxidant potential on human health, suggesting that their high content in apple is responsible for the beneficial effects of apple consumption. They are also linked to the quality of apple juices and ciders since they are predominantly responsible for astringency, bitterness, color and aroma. Major phenolic compounds were quantified by liquid chromatography in fruits and juices from a cider apple progeny harvested for three years. The total content of procyanidins and their average degree of polymerization (DPn) were also determined in fruits by phloroglucinolysis. Variability and extraction yield of these compounds were determined. RESULTS: The variability observed in the progeny was representative of the variability observed in many cider apple varieties. Hydroxycinnamic acids were the most extractable group, with an average extraction yield of 67%, whereas flavonols and anthocyanins were the least. CONCLUSION: This study is the first one to introduce variability and extraction yields of the main phenolic compounds in both fruits and juices of a cider apple progeny. This dataset will be used for an upcoming QTL mapping study, an original approach that has never been undertaken for cider apple

QTL mapping and candidate gene research for the phenolic content of fruits and juices prepared from a cider apple progeny

Polyphenols have favorable antioxidant potential on human health suggesting that their high content in apple is responsible for the beneficial effects of apple consumption. They are also related to the quality of ciders as they predominantly account for astringency, bitterness, color and aroma. Five groups of phenolic compounds are described in the apple fruit: flavanols, hydroxycinnamic acids, dihydrochalcones, flavonols and anthocyanins. So far, only two studies have been published on the genetic basis of the phenolic content of dessert apples. As cider apples are commonly described to be much more concentrated in phenolic compounds than dessert varieties, the present study focuses on a cider apple progeny. 32 compounds belonging to the five groups were identified and quantified by HPLC-UV and UHPLC-UV-MS/MS in fruit extracts and juices. 53 QTL controlling phenolic compounds concentration were detected on nine linkage groups (LG) on the integrated linkage map, for all phenolic groups except anthocyanins. QTL clusters located on LG1, 12, 14, 15 and 17 were stable across the year or the studied material. QTL detected on LG1, 14 and 17 for quercitrin, p-coumaroylquinic acid, rutin and chlorogenic acid confirmed results of previous studies. However, no significant QTL was obtained on the LG16 where a major locus for flavanols was previously located. With the two previous studies, this study shows the diversity of genomic regions controlling traits of interest in apple.Cartographie génétique des composés phénoliques de la pomm

QTL Analysis and Candidate Gene Mapping for the Polyphenol Content in Cider Apple

Polyphenols have favorable antioxidant potential on human health suggesting that their high content is responsible for the beneficial effects of apple consumption. They control the quality of ciders as they predominantly account for astringency, bitterness, color and aroma. In this study, we identified QTLs controlling phenolic compound concentrations and the average polymerization degree of flavanols in a cider apple progeny. Thirty-two compounds belonging to five groups of phenolic compounds were identified and quantified by reversed phase liquid chromatography on both fruit extract and juice, over three years. The average polymerization degree of flavanols was estimated in fruit by phloroglucinolysis coupled to HPLC. Parental maps were built using SSR and SNP markers and used for the QTL analysis. Sixty-nine and 72 QTLs were detected on 14 and 11 linkage groups of the female and male maps, respectively. A majority of the QTLs identified in this study are specific to this population, while others are consistent with previous studies. This study presents for the first time in apple, QTLs for the mean polymerization degree of procyanidins, for which the mechanisms involved remains unknown to this day. Identification of candidate genes underlying major QTLs was then performed in silico and permitted the identification of 18 enzymes of the polyphenol pathway and six transcription factors involved in the apple anthocyanin regulation. New markers were designed from sequences of the most interesting candidate genes in order to confirm their co-localization with underlying QTLs by genetic mapping. Finally, the potential use of these QTLs in breeding programs is discussed

Profiling of tannins, flavonoids and hydroxycinnamic esters in the fruits of a cider apple progeny

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Properties of polymorphic SSR primers developed from ‘Golden Delicious’ genomic sequence for major candidate genes.

<p>*: enzymes which could not be mapped.</p>a<p>: F3’H: flavonoid 3′-hydroxylase; F3'5'H: flavonoids 3',5'-hydroxylase; FHT: flavanone 3-β-hydroxylase; UFGT: UDP-glucose 3-glucosyltransferase; DFR: dihydroflavanol 4-reductase; FLS: flavonols synthase; CHI: chalcone isomerase; CHS: chalcone synthase; HCT/HQT: shikimate/quinate hydroxycinnamoyltransferase.</p><p>Properties of polymorphic SSR primers developed from ‘Golden Delicious’ genomic sequence for major candidate genes.</p

Phenolic compounds biosynthesis [15]–[20] (KEGG, 2012).

<p>In bold, enzymes identified in the support interval of QTLs. 4CL: 4-coumarate:CoA ligase; ANR: anthocyanidin reductase; ANS: anthocyanidin synthase; C3'H: <i>p</i>-coumarate 3′-hydroxylase; C4H: cinnamate 4-hydroxylase; CHI: chalcone isomerase; CHS: chalcone synthase; D2'GT: dihydrochalcone 2-<i>O</i>-glucosyltransferase; DFR: dihydroflavanol 4-reductase; F3'H: flavonoid 3′-hydroxylase; F3'5'H: flavonoid 3',5'-hydroxylase; FHT: flavanone 3-β-hydroxylase; FLS: flavonol synthase; HCT: shikimate <i>O</i>-hydroxycinnamoyl transferase; HQT: quinate <i>O</i>-hydroxycinnamoyl transferase; LAR: leucoanthocyanidin reductase; PAL: phenylalanine ammonia lyase; TAL: tyrosine ammonia lyase; UFGT: UDP-glucose 3-glucosyltransferase.</p

Main interesting clusters of quantitative trait loci (QTL) for phenolic compounds in fruit and juice.

<p>Main QTL clusters obtained are represented with black bars on the right of the corresponding linkage groups (LG). Putative candidate genes identified <i>in silico</i> and their relative position on the map are specified on the left of the LG. Genetically mapped candidate genes are indicated on the right of the LG and underlined.</p

Broad sense genetic heritability of mean polymerization degree and phenolic compounds quantified in fruits harvested in 2008 (F08) and 2009 (F09) and in juices prepared in 2009 (J09) and 2010 (J10).

a<p>: DPn: mean polymerization degree.</p>b<p>: na: not available.</p><p>Broad sense genetic heritability of mean polymerization degree and phenolic compounds quantified in fruits harvested in 2008 (F08) and 2009 (F09) and in juices prepared in 2009 (J09) and 2010 (J10).</p

Selected candidate genes identified in the interval of 12 clusters of quantitative trait loci (QTL) using the BLAST2GO software.

a<p>: CHI: chalcone isomerase; CHS: chalcone synthase; DFR: dihydroflavanol 4-reductase; F3'H: flavonoid 3′-hydroxylase; F3'5'H: flavonoids 3',5'-hydroxylase; FLS: flavonols synthase; HCT/HQT: shikimate/quinate hydroxycinnamoyl transferase; UFGT: UDP-glucose 3-glucosyltransferase.</p>b<p>: contig containing the gene on the apple genome browser.</p>c<p>: longest hits which aligned with the sequence.</p>d<p>: numbered of alignment achieved.</p>e<p>: estimator of the quality of the alignment.</p>f<p>: average proportion of sequence similarity.</p><p>Selected candidate genes identified in the interval of 12 clusters of quantitative trait loci (QTL) using the BLAST2GO software.</p

Quantitative trait loci (QTL) detected in the apple X5210 and X8402 parental genetic maps by multiple QTL mapping (MQM) analysis and Kruskal-Wallis (KW) test for phenolic compounds and the mean polymerization degree of flavanols estimated in fruits harvested in 2008 and 2009 and in juices prepared in 2009 and 2010.

a<p>: Maximum logarithm of the odds (LOD) scores value of the QTL.</p>b<p>: Proportion of the phenotypic variation explained by the QTL.</p>c<p>: results of the Shapiro-Francia normality test calculated with the residuals obtained after QTL detection.</p>d<p>: *, P = 0.1; **, P = 0.05; ***, P = 0.01.</p><p>Quantitative trait loci (QTL) detected in the apple X5210 and X8402 parental genetic maps by multiple QTL mapping (MQM) analysis and Kruskal-Wallis (KW) test for phenolic compounds and the mean polymerization degree of flavanols estimated in fruits harvested in 2008 and 2009 and in juices prepared in 2009 and 2010.</p