S01 - Session O7 - Genetic architecture of agronomic traits in Stevia rebaudiana

Authors: Charles Bastide *, Zoé Le-Bihan, Patrick Cosson, Galadriel Briere, Erwan Guichoux, Alexis Groppi, Dominique Rolin, Valérie Schurdi-Levraud, Raluca Uricaru

Stevia rebaudiana (Asteraceae) is a perennial plant native to Paraguay that is cultivated throughout the world for steviol glycoside (SG) production. These acaloric molecules have a sweetening power 300 times greater than that of sucrose. Being an orphan species for a long time, its genome was sequenced only very recently. Its genetic improvemet is also in its infancy. In order to be able to offer farmers in the south-west of France genotypes adapted to organic farming conditions, we have gathered worldwide a collection of 145 genotypes, developed EST-SSR and SNP molecular markers, and analysed the genetic and phenotypic diversity of this collection of genotypes. On the basis of two fundamental traits for the economic sustainability of this crop, yield of sweet steviol glycosides and response to Septoria spp, 6 parents were selected and crossed. Two half-sib populations were analysed over 3 years, enabling the estimation of genetic parameters of yield-related traits, confirming an increase over the years of these traits and selecting elite individuals among these populations. SSR marker identification was performed using the Compositae Genome Project of UC Davis, and supplemented by SSR marker detection by Warner and Bhandawat. An adaptated SNP calling pipeline was developed by using a reduced-representation library (RRL) sequencing allowing the identification of SNP markers. Furthermore, we performed sequencing, which identified 28 SEQSSRs. Together with this information, the genetic map of these crosses has been established. The detection of QTLs associated with sweet SG yield and response to Septoria spp. will be presented. This work allows us to consider the optimisation of breeding strategies in Stevia rebaudiana , in particular for the response to pathogens, a trait that has never been taken into account in breeding strategies.