Plant & Animal Genome IX Conference

Workshop: Aquaculture
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DEVELOPMENT OF A GENETIC MAP IN THE PACIFIC OYSTER, Crassostrea gigas, USING 11 DAY OLD LARVAE.

Bodega Marine Laboratory, University of California at Davis, P.O. Box 247, Bodega Bay, CA 94923, USA

The Pacific oyster, Crassostrea gigas, is one of the most important species in aquaculture. The development of a genetic map using microsatellite markers will allow QTL mapping which can benefit breeding program. Four outbreed families were produced from parents with known pedigrees. Four microsatellite-enriched libraries were constructed, two libraries of di-nucleotide repeat (CA and GA), one of tri-nucleotide repeat (TAG) and one of tetranucleotide repeat (TAGA). From these libraries, we are sequencing 500 clones for designing PCR-primers. So far of 26 sequenced clones from the four libraries, 13 new microsatellite markers proved useful. Each new microsatellite marker is tested on grand parents and parents of four oyster families. This allows us to know the linkage phase and to determine if this locus can be mapped. Trisomic oyster families will be used to assign linkage groups to specific chromosomes. Distortion of Mendelian segregation ratios has been widely reported in bivalves, but it has been shown by Launey and Hedegecok (1999) that no distortion occurs in 6-h-old larvae. Segregation in 11 day old larvae were studied with five of the new microsatellites, 18 from Launey et Hedgecock (1999) and two from English et al. (in prep.). One family has been tested and no microsatellite markers showed a distortion of segregation. Eleven day old larvae provide sufficient DNA after a proteinase-K extraction for 50 PCR reactions allowing more linkage tests per individuals than with 6-h-old larvae.

• Launey S. and Hedgecock D.1999. Genetic load causes segregation distorsion in oysters : Mapping at 6 hours. PAG VII, abstract W14.