Marker-Assisted Selection

Marker-assisted selection (MAS) uses one or a few DNA markers that are statistically linked to a gene of major effect on a trait of economic interest, allowing breeders to select fish carrying the favorable allele directly from a fin clip rather than from a full phenotype. Classic aquaculture examples include selection for disease resistance loci such as the major QTL for infectious pancreatic necrosis resistance in Atlantic salmon, and for flesh color genes influenced by carotenoid metabolism. MAS is most efficient when a single locus explains a large share of trait variation, typically more than 10 to 20% of genetic variance; for polygenic traits like overall growth it is less powerful than family selection or genomic selection. The workflow is practical for hatcheries: genotype juvenile candidates, retain carriers, and combine MAS with conventional performance data. Limitations include linkage breakdown over generations, which requires periodic marker validation, and the risk of losing background genetic progress by focusing selection on one locus. MAS remains cheaper than genome-wide genomic selection and is a sensible entry point for mid-size breeding programs. It interlocks with family selection, genomic selection, and sex determination work, since several commercially important markers are located on sex chromosomes.