S01 - Session P10 - Harnessing molecular data to support DUS testing in ornamentals: a case study on Hydrangea

Authors: Marc Delêtre, Muriel Thomasset *, Stéphanie Christien, Arnaud Remay

Hydrangeas, one of the world's most popular ornamental flowers, are a major horticultural crop and one of the most economically important ornamental plants in France. Maine-et-Loire alone represents 25% of the European production. GEVES (Groupe d'Etude et de controle des Varietes Et des Semences) is responsible for the national collection of Hydrangea , an in vivo reference collection of over 1,500 taxa maintained at the Gaston-Allard Arboretum in Angers. GEVES and the Bundessortenamt in Germany are the only two examination offices entrusted by CPVO for DUS (Distinction, Uniformity, Stability) examination in Hydrangeas in the framework of the European Plant Breeders Rights. DUS examinations are carried out over a 2-year period. In the first year, reference varieties are chosen based on the candidates' characteristics as listed in the technical questionnaire. To facilitate assessment of distinctness, candidates and references are divided into groups based on their main morphological characteristics. As the number of applications grows, so does the size of the reference collection, hence the number of reference varieties within each group increases every year. Hydrangea DUS testing is constrained in terms of space as plants have to be grown in shadehouses. A means to select only the most appropriate reference varieties would help keep the size of trials within these technical constraints. In 2022, GEVES and BSA will start an 18-months joint project co-funded by CPVO to use high-throughput sequencing technologies for developing a molecular toolset that can be used to build a comprehensive genetic reference dataset for the reference collection of Hydrangeas. This molecular library will help securing DUS trials and optimizing the use of otherwise limited space by: (1) checking the varietal identity of reference varieties before starting DUS tests, and (2) facilitating the selection of the most appropriate reference varieties, with which to compare the candidates.