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Breeding new cultivars is an important lever to cope with the various challenges facing viticulture. As a prerequisite, it is necessary to assess how much genetic variation is available for the traits of interest, and to understand their genetic architecture. To go beyond quantitative trait locus (QTL) mapping in biparental crosses, we exploited the panel of 279 cultivars capturing most of the genetic and phenotypic diversity of Vitis vinifera L. present within the French collection of genetic resources (INRA Vassal). This panel was planted in the vineyard in five randomized complete blocks and numerous traits (berry weight, cluster weight, length and compactness, organic acids, δ13C, polyphenols, etc.) were phenotyped over several years. In parallel, the panel was genotyped with the GrapeReSeq microarray as well as with restriction-assisted DNA sequencing. This allowed us to conduct a genome-wide association study per trait, either by testing each single-nucleotide polymorphism (SNP) separately or by modeling all SNPs jointly. Focusing here on berry weight, we showed that genotyping by sequencing provided enough SNPs to explain most of the genetic variance, and that, compared with SNP-by-SNP approaches, a multi-SNP statistical model led to a gain in power. Several significant associations were detected, some being new compared with the QTLs detected in biparental crosses. Future prospects include setting up an international consortium to plant the panel on various sites to help to decipher genotype-environment interactions.

Since 1997, many studies have been performed based on the inheritance of nuclear microsatellite markers to verify or uncover the parentage of several grapevine cultivars. The aim of the present study was to undertake an extended analysis using a large sample of Vitis vinifera cultivars held in the INRA ?Domaine de Vassal? Grape Germplasm Repository (F-34340 Marseillan-Plage, France). We genotyped 5,516 accessions with 20 nuclear SSR markers and checked their identity. The dataset of 2,332 single genotypes identified (without synonyms, clones and mutants) was analyzed using FaMoz software. Parentages showing a LOD score higher than 18 were validated in relation to historical data available. The parentage analysis first permitted the identification of 284 genotypes showing no direct relationship with any other cultivar in the collection. Second, in approx. 1,150 genotypes, only incomplete parentages could be determined due to the absence of complementary parents in the cultivar sample. Last, the full-parentage of approx. 700 genotypes was revealed resulting in i) confirmations of the pedigree as stated by the breeder (180) or in previously published studies (80), ii) partial or complete invalidations of published pedigree (90), or iii) original discoveries (390). Compiling these parentage results improves our knowledge of the genetic constitution of the population of V. vinifera cultivars and the identification of the main genitors involved in varietal assortment evolution and grapevine breeding.