Diversité génétique chez les huîtres creuses du genre Crassostrea : quelles ressources pour quelle amélioration des productions de C; gigas?

Despite the economic importance of oyster farming, knowledge about genetic resources of these species is still limited. The objectives of my research were to provide further information about (1) taxomomy, phylogeny and phylogeography of Crassostrea oysters, (2) to compare C. gigas and C. angulata strains of various geographic origins and (3) to study phenotypic and genetic variation for traits of aquacultural interest in C. gigas. Studies based on DNA polymorphism and chromosomes allowed to improve or correct identification, geographic range and phylogeographic relationships among several species. The comparison of various strains of C. gigas and C. angulata, both in laboratory and field conditions, revealed significant differences among taxa and the better adaptation of European strains to local conditions. C. gigas showed a large phenotypic and genetic variability for traits of interest for aquaculture. The observed variability for traits related to resource allocation and their correlation, together with the specific conditions of spat production in hatchery might explain why such a variation is observed for fitness-related traits. The development of selective breeding programmes, based on French C. gigas populations, should lead to efficient improvement of the oyster production.