Fisheries, Animal, and Veterinary Science
Eastern oyster; SNP; Dermo; polymorphism
Oysters are a keystone species; they are filter-feeders and reef-builders. Additionally, oysters are extremely important within the shellfish aquaculture industry; they are the second most widely produced species in world aquaculture production. Eastern oysters, Crassostrea virginica, are produced in aquaculture and are unfortunately susceptible to Dermo disease. Dermo is caused by a protozoan parasite, Perkinsus marinus, and infection is often fatal in oysters due to widespread tissue damage and blockage of blood vessels. Research in oyster disease is particularly needed because disease is one of the largest impediments faced by the aquaculture industry as entire oyster populations can be decimated. One of the best options for prevention of Dermo involves identifying oysters with genetic resistance to the disease and breeding them for aquaculture use.
In order to rapidly and effectively breed oysters for disease resistance, links between disease resistant genotypes and phenotypes must be established. To date, only one gene has been associated repeatedly with Dermo resistance in the eastern oyster: the serine proteinase inhibitor 1 gene (CvSI-1). Proteinase inhibitors are known to play a role in immunity; hence an alteration in these genes, such as a SNP, can have functional consequences. The focus of this research project involved developing an assay for genotyping a single nucleotide polymorphism (SNP) within the CvSI-1 gene and confirming its association with disease resistance in two selected oyster populations. Development of the genotyping assay involved the identification of individuals to use as positive controls (known genotypes at the CvSI-1 SNP198 locus) via amplification and sequence analysis. Once positive controls were identified, additional samples, collected before and after a natural Dermo outbreak, were genotyped using a high resolution melting (HRM) assay. Melting curves from all samples were compared to positive controls to assign genotypes. Genotype and allele frequencies were used to identify shifts following selection by Dermo. A significant difference in allele frequencies before and after Dermo induced mortality suggests the CvSI-1 SNP198 locus is associated with resistance.