Background: The economic importance of grapevine has driven significant efforts in genomics to accelerate the exploitation ofVitisresources for development of new cultivars. However, although a large number of clonally propagated accessions are maintained in grape germplasm collections worldwide, their use for crop improvement is limited by the scarcity of information on genetic diversity, population structure and proper phenotypic assessment. The identification of representative and manageable subset of accessions would facilitate access to the diversity available in large collections. A genome-wide germplasm characterization using molecular markers can offer reliable tools for adjusting the quality and representativeness of such core samples.Results: We investigated patterns of molecular diversity at 22 common microsatellite loci and 384 single nucleotide polymorphisms (SNPs) in 2273 accessions of domesticated grapevineV. viniferassp.sativa, its wild relativeV. viniferassp.sylvestris, interspecific hybrid cultivars and rootstocks. Despite the large number of putative duplicates and extensive clonal relationships among the accessions, we observed high level of genetic variation. In the total germplasm collection the average genetic diversity, as quantified by the expected heterozygosity, was higher for SSR loci (0.81) than for SNPs (0.34). The analysis of the genetic structure in the grape germplasm collection revealed several levels of stratification. The primary division was between accessions ofV. viniferaand non-vinifera, followed by the distinction between wild and domesticated grapevine. Intra-specific subgroups were detected within cultivated grapevine representing different eco-geographic groups. The comparison of a phenological core collection and genetic core collections showed that the latter retained more genetic diversity, while maintaining a similar phenotypic variability.Conclusions: The comprehensive molecular characterization of our grape germplasm collection contributes to the knowledge about levels and distribution of genetic diversity in the existing resources ofVitisand provides insights into genetic subdivision within the European germplasm. Genotypic and phenotypic information compared in this study may efficiently guide further exploration of this diversity for facilitating its practical use.

High fruit and wine quality combined with good climatic adaptation and disease resistance are essential objectives of grape breeding. While several molecular markers are available for pyramiding resistance to fungal pathogens, molecular tools for predicting fruit composition are still scarce. Muscat flavor, caused by the accumulation of monoterpenoids in the berry, is an important target trait for breeding, sought after in both table grapes and wine. Four missense mutations in the VvDXS gene in grape germplasm have been shown to be tightly linked to muscat flavor. Here we present highly reproducible and breeder-friendly functional markers for each of the targeted polymorphisms developed by using either the multiplexed minisequencing SNaPshot™ method, the high-resolution melting (HRM) assay or the cleaved amplified polymorphic sequence system. A total of 242 grapevine accessions were analyzed to optimize these different genotyping methods and to provide allele-specific markers for accurate selection of muscat flavor at early stages of grape breeding programs. The HRM and the minisequencing SNaPshot multiplex assays allow for high-throughput automated screening and are suitable for large-scale breeding programs and germplasm characterization.

The IFAPA research center “Rancho de la Merced” (Jerez, Spain) hosts one of the oldest and most diverse grapevine germplasm repositories in Europe, and is aimed at providing feasible solutions to deal with any agronomic trait by exploring its genetic variability and by means of association and Deoxyribonucleic Acid (DNA) editing studies. In this work, we focused on a wine and dual-use grapevine subcollection that consists of 930 accessions. Genetic analysis allowed to identify 521 unique genotypes. After comparing them with several databases, matches were found for 476 genetic profiles while the remaining 45 have not been previously described. Combination with clustering analysis suggested a total pool of 481 Vitis vinifera accessions that included some table cultivars. Several synonymies, homonymies and mislabeling have also been detected. Structure analysis allowed identifying six clusters according to eco-geographic cultivation areas and one additional group including non-vinifera accessions. Diversity analysis pointed out that Spanish Mediterranean varieties are genetically closer to oriental genotypes than to European varieties typical of oceanic and continental climates. The origin of Spanish varieties is discussed in depth considering our data and previous studies. Analysis of molecular variance partition confirmed a well-structured germplasm, although differentiation among groups had a much lower effect on genetic variability than differences within groups, which are strongly related to a very high heterozygosity. A core collection that covers all allele richness is proposed. It is constituted of about 13% of total accessions, and each cluster inferred by structure analysis is represented.

Editorial: Interdisciplinary approaches to improve quality of soft fruit berries, volume II

ISHS IX International Strawberry Symposium Development of a new phenotypic roadmap to improve strawberry aroma based on direct injection mass spectrometry

ISHS I International Symposium on Grapevine Roots Methods to dissect grapevine rootstocks responses to drought stress