A first genetic linkage map of the European flat oyster, Ostrea edulis : towards the identification of Bonamia resistance QTLs
2007
Lallias, Delphine | Lapegue, Sylvie | Haley, Chris | Heurtebise, Serge | Boudry, Pierre | Beaumont, Andy
The flat oyster Ostrea edulis is an endemic European oyster species, found on both Atlantic and Mediterranean coasts. Its aquacultural production has dramatically decreased due to two successive diseases caused by the intracellular parasites Marteilia refringens and Bonamia ostreae. Since 1985, Ifremer has undertaken a breeding program to produce oyster families which are tolerant to Bonamia. In this context, the next step is to identify QTLs for resistance to this parasite. A genetic map is therefore being established as a basis for QTL work. The reference family is an F2 family produced by single pair mating of two oysters from the same F1 family. The F1 family was itself produced from a bi-parental cross between a wild oyster and an individual from the fifth generation inbred line of the Bonamia tolerance selection program. This inbred line had shown no mortality when reared in sites where the parasite was present. Ninety-two progeny were used for linkage analysis in this study. Twenty microsatellites and 60 AFLP (Amplified Fragment Length Polymorphism) primer pairs were scored. Linkage analysis was carried out using CRIMAP v.2.4. Among the polymorphic markers, 296 AFLPs segregated in the mapping family: 235 were used in the linkage analysis (all the 1:1 and the Mendelian 3:1 markers) and 16 microsatellites. The linkage map of the first parent consisted of 137 markers grouped into 8 linkage groups (2n=20). The linkage map of the second parent consisted of 149 markers grouped into 9 linkage groups with more than 5 markers and 3 doublets. Moreover, three sex-average linkage groups were built with more than 3 microsatellites as anchor loci. Average marker spacing was 6 cM and length spanned from 69 to 98 cM. Once the genetic linkage map has been drawn, it will provide a foundation for identifying parasite tolerance QTLs.
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