Plant, Animal & Microbe Genomes X Conference Plant, Animal & Microbe Genomes X ConferenceJanuary 12-16, 2002
Town & Country Convention Center
San Diego, CA
Workshop: Aquaculture
Oyster diseases have devastated natural populations of the eastern oyster, motivating development of selective breeding strategies for enhancing disease resistance. Microsatellite markers are being used to construct a genetic linkage map with the aim of identifying molecular markers linked to disease resistance loci for use in marker-assisted selection programs. Primers for use in the polymerase chain reaction were designed to amplify di-, tri- and tetra- nucleotide microsatellite regions of the Crassostrea virginica genome. Microsatellite loci were identified that contain either perfect, imperfect or compound repeat sequences. Non-Mendelian segregation ratios and null alleles are often observed in studies utilizing molecular markers for genetic analyses of molluscan species. Analysis of eight markers in four full-sib reference families of the eastern oyster revealed significant deviations from expected Mendelian segregation ratios in three of twenty-six tests after sequential Bonferroni correction. Non-Mendelian ratios were found both in the direction of heterozygote excess and deficiency. Indeed, in one family, deficiencies in both a heterozygotic and homozygotic genotype were observed at a single locus. Null alleles were detected at five of nineteen loci and primers are being redesigned to enable elucidation of these alleles. In addition, markers are being surveyed for use in genetic monitoring of oyster reef restoration projects, which may employ oysters bred for disease resistance through traditional selective breeding techniques. Overall, disease resistant stocks show reduced genetic variation compared to natural populations. Genotyping at seven microsatellite loci allows assignment of individuals to either selected stocks or wild populations with 95% confidence.