||Lallias Delphine, Beaumont Andy, Haley Chris, Heurtebise Serge, Boudry Pierre, Lapegue Sylvie
||Plant & Animal Genome Conference
||QTLs, Flat oyster, Ostrea edulis, Bonamia ostreae, Genetic, QTL
||A breeding programme has been undertaken by Ifremer to produce selected Ostrea edulis families which are resistant to Bonamia ostreae, a parasite which is the most significant constraint on aquaculture of this oyster. Using such families, we aimed to identify Quantitative Trait Loci (QTLs) of resistance/susceptibility to bonamiosis. We used an F2 family derived from a bi-parental cross between a wild oyster and an individual from one of the selected oyster families. A total of 550 F2 individuals from the family cohabited with wild oysters that were injected with the parasite. Mortality was checked daily over six months and heart smears were used on moribund or dying oysters to detect the presence and level of infection of the parasite. Ninety two F2 progeny were scored for 20 microsatellites and 34 AFLP primer pairs: 46 were heavily infected oysters that died during the challenge experiment and 46 were oysters that survived and in which no parasite could be detected. Sex-specific genetic linkage maps were built for the family, spanning 10 linkage groups (n=10) with an observed genome coverage of 69-84%. Fifteen AFLPs (out of 304) showed a significant difference of allele frequencies between the two phenotypically extreme groups. A QTL interval mapping approach identified 3 QTLs in the first parental map and 2 in the second. Some of the 15 markers identified in the survival analysis were mapped to the same locations as the QTLs, strengthening our results.