Gaining insight into the history of grapevine varieties through DNA analysis Molecular markers have been highly effective in studies on grapevine varieties, especially in the 1990s with the use of microsatellite markers, or simple sequence repeats (SSRs). These molecular tools have generated knowledge on three topics related to the history of grapevine varieties, i.e. their identification, genealogy, and the geographical structure of their diversity.
of comparative morphological studies. The positioning of varieties in these diversity groups at different scales has clarified their possible geographical origins and historical pathways. Contacts: Thierry Lacombe, lacombe@supagro.inra.fr Jean-Michel Boursiquot, jean-michel.boursiquot@supagro.fr
Varietal identification has benefitted substantially from the availability of molecular markers to back conventional ampelographic techniques. Many local, national and international studies have led to the confirmation or discovery of synonymous and homonymous varietal names, thus boosting insight into current and past ranges of certain ‘traveller’ grapevine varieties. These synonyms are now pooled in several online open access databases. Genealogical studies began in 1993. Since then, several studies have confirmed or refuted hybridization data supplied by breeders, but more importantly they have revealed the pedigree of much older traditional varieties. This is how the parents of famous varieties —Chardonnay, Merlot, Syrah, etc.—were revealed. These results highlighted certain major parents in the past but which are no longer found in modern day vineyards (Gouais blanc, Magdeleine noire des Charentes, Mondeuse blanche, etc.). Diversity studies conducted at local, national or international scales have clarified the geographical origin of grapevine varieties beyond their direct genealogical origin. They led to the proposal of several diversity groups, some of which had not been suspected on the basis
Network representing half-kinship relationships revealed in 2 344 grapevine varieties in the Domaine de Vassal collection based on 20 microsatellite markers Wine grape varieties are shown in blue, table grape varieties in yellow, and dual-purpose varieties in green, while black lines symbolize kinship. © T. Lacombe, J.-M. Boursiquot,V. Laucou, M. Di Vecchi-Stara, J.-P. Peros, P. This
t A microvine plant (dwarf grapevine) with inflorescences at different development stages along the main stem © L. Torregrosa/UMR AGAP, DAAV research team.
With the aim of identifying genomic regions and if possible genes involved in traits of interest, UMR AGAP conducts research in different populations to find statistical associations between genotypic variation of many markers distributed throughout the genome (DNA polymorphism) and phenotypic variation in traits measured on plants. These populations are derived from isolated or interconnected crosses (with common parents, e.g. in a diallel design), thus enabling comparison of results in different genetic backgrounds. The research unit also uses samples of unrelated varieties to more quickly and thoroughly investigate the available variability (association genetics). Plants are grown in the field or in pots to facilitate studies on the genetic bases of adaptation to water and heat stresses. In particular, studying a short-cycle dwarf progeny (microvines, see photo) allowed the entire population to be grown in a growth chamber under two different temperature regimes. New genomic regions involved in variations in berry weight and acid concentration over a broad temperature range were thus found. As many genes are present in these regions, screening based on the expression and variability profiles of these genes is thus necessary. When a gene is found to be a very likely candidate to explain the trait variability, functional genomics can be used to try to validate its effects on the trait. Contacts: Agnès Doligez, agnes.doligez@supagro.inra.fr Laurent Torregrosa, laurent.torregrosa@supagro. fr Charles Romieu, charles.romieu@supagro.inra.fr
Viticulture and Wine
Identification of the genetic bases of grapevine quality and adaptation
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