Résumé
The European flat oyster, Ostrea edulis, occurs naturally from Norway to Morocco in the North-Eastern Atlantic and throughout the Mediterranean. The oyster has been a harvested species for at least 6000 years. However, it successively suffered from over harvesting and then from two protozoan diseases during the 1960s and its production has drastically decreased in Europe from that time. Following two generations of selection for tolerance to one of these diseases (bonamiosis), our aim is to optimize this selection with the assistance of molecular markers, that is to say to implement marker-assisted selection. This will enhance the efficiency of selection by reducing the generation time, as the selection on sites cannot be made before the oysters are three-years old. The establishment of the genetic linkage map represents the foundation for the identification of QTLs (Quantitative Trait Loci : markers linked to genes involved in quantitative parameters such as growth rate and parasite tolerance). Map building consists of the ordering of genetic marker loci and estimating relative distances between them, using data from individuals in an appropriate family structure. Therefore, we have chosen to follow the segregation of markers in two experimental families.