A candidate gene association study on muscat flavor in grapevine (Vitis vinifera L.)

Francesco Emanuelli,Loïc Le Cunff,Jean-Michel Boursiquot,Patrice This,Laura Costantini,Maria S Grando,Juri Battilana

doi:10.1186/1471-2229-10-241

Francesco Emanuelli, Loïc Le Cunff + Show 5 more

Open Access

https://doi.org/10.1186/1471-2229-10-241

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Abstract

BackgroundThe sweet, floral flavor typical of Muscat varieties (Muscats), due to high levels of monoterpenoids (geraniol, linalool and nerol), is highly distinct and has been greatly appreciated both in table grapes and in wine since ancient times. Muscat flavor determination in grape (Vitis vinifera L.) has up to now been studied by evaluating monoterpenoid levels through QTL analysis. These studies have revealed co-localization of 1-deoxy-D-xylulose 5-phosphate synthase (VvDXS) with the major QTL positioned on chromosome 5.ResultsWe resequenced VvDXS in an ad hoc association population of 148 grape varieties, which included muscat-flavored, aromatic and neutral accessions as well as muscat-like aromatic mutants and non-aromatic offsprings of Muscats. Gene nucleotide diversity and intragenic linkage disequilibrium (LD) were evaluated. Structured association analysis revealed three SNPs in moderate LD to be significantly associated with muscat-flavored varieties. We identified a putative causal SNP responsible for a predicted non-neutral substitution and we discuss its possible implications for flavor metabolism. Network analysis revealed a major star-shaped cluster of reconstructed haplotypes unique to muscat-flavored varieties. Moreover, muscat-like aromatic mutants displayed unique non-synonymous mutations near the mutated site of Muscat genotypes.ConclusionsThis study is a crucial step forward in understanding the genetic regulation of muscat flavor in grapevine and it also sheds light on the domestication history of Muscats. VvDXS appears to be a possible human-selected locus in grapevine domestication and post-domestication. The putative causal SNP identified in Muscat varieties as well as the unique mutations identifying the muscat-like aromatic mutants under study may be immediately applied in marker-assisted breeding programs aimed at enhancing fragrance and aroma complexity respectively in table grape and wine cultivars.

Highlights

The sweet, floral flavor typical of Muscat varieties (Muscats), due to high levels of monoterpenoids, is highly distinct and has been greatly appreciated both in table grapes and in wine since ancient times
We assessed the association of nucleotide variation in the candidate gene VvDXS with muscat flavor in grapevines with different genetic backgrounds
Validation of the candidate gene VvDXS expression into Muscat genetic background In order to determine if the candidate gene VvDXS was expressed in the grape berry of Moscato Bianco, we amplified the full-ORF VvDXS cDNA from the cDNA retrotranscribed from total RNA of berry skin

Summary

Introduction

The sweet, floral flavor typical of Muscat varieties (Muscats), due to high levels of monoterpenoids (geraniol, linalool and nerol), is highly distinct and has been greatly appreciated both in table grapes and in wine since ancient times. Muscat flavor determination in grape (Vitis vinifera L.) has up to now been studied by evaluating monoterpenoid levels through QTL analysis. These studies have revealed co-localization of 1-deoxy-Dxylulose 5-phosphate synthase (VvDXS) with the major QTL positioned on chromosome 5. The floral flavor typical of Muscat varieties ( known as Muscats) is highly distinct and has been greatly appreciated since ancient times. The primary monoterpene skeleton can be further modified by the action of various enzymes (i.e. cytochrome P450 hydroxylases, dehydrogenases and glycosyl and methyltransferases) [9,10]

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