S05 - Session P6 - Exploring the Rosa genetic diversity through the 20th century with an interdisciplinary approach

Authors: Agnes Grapin *, Jeremy Clotault, Jordan Marie-Magdelaine, Annie Chastellier, Fabrice Foucher, Tatiana Thouroude, Cristiana Pavie, Blandine Veith, Alix Pernet

During the 19th century, roses became one of the leading ornamental plants. Our previous work showed that rose diversity was shaped by both biological and cultural factors. Transcontinental circulation of plants between Asia and Europe permitted to introduce in breeding a key ornamental trait, the recurrent blooming, and led to a shift in the structure of genetic diversity, from the old European background to an Asian one. This trend brought out a tension between the continuous search for novelties, underpinned by the commercial success of roses, and the preservation of older cultivars through vegetative propagation in collections. The aim of this work is to characterize the genetic diversity of roses bred during the 20th century considering two competing phenomena: the global scale of commodification and the emergence of heritage/heirloom cultural practices. This study involves a cross-disciplinary collaboration between geneticists and social scientists. The first step was to establish the composition of a large sample of roses which could represent the whole history of the period (before or after World War II, globalization of trade, interest for old fashioned flowers…), the different market sectors (garden, cut flowers, pot) and many breeders. Thus, a sample of 1800 accessions, 1600 of them being varieties obtained from 1900 to 2017, were prospected, documented, and genotyped with 24 microsatellite primer pairs. These markers were used to characterize the genetic structure of the sample and measure the extent of its diversity. Rose genetic diversity continued to evolve along the 20th century. The main results will be presented and discussed in regards to historic and socio-economic facts as breeders' life stories and production management.