MICROSATELLITES: Tool of Choice for Aquaculture

Microsatellites: Tool of Choice for Aquaculture**

Genetic Markers for the Future

1994 Summary by Jonathan M. Wright and Paul Bentzen

(Marine Gene Probe Laboratory, Dalhousie University, Halifax, Nova Scotia, CANADA)

1. Microsatellites are very abundant and spread over the entire genome of all living organisms, so markers can be readily developed for any genetic objective.
2. Some microsatellites exhibit extremely high levels of allelic (DNA components) variation. This attribute makes microsatellites especially attractive in a number of applications which include:

• Species that show low overall levels of genetic variation.
• Populations that are inbred.
• Recently derived or geographically close populations where genetic differentiation may be limited or difficult.
• Pedigree analysis and tracking.

1. Microsatellite alleles are co-dominant markers. That is, they can be tracked in both sexes, but trait expression may only show up in one gender.
2. Microsatellites are assayed using PCR (Polymerase Chain Reaction), so only minute amounts of tissue are required. This tool is non-intrusive (non-lethal) to the animal and allows us to use the animal at a later time for breeding purposes.
3. Microsatellites can be assayed more rapidly than other types of molecular marker approaches. The high allelic nature of microsatellites means that they confer more information per unit assay than any other marker systems, thus reducing costs.
4. Microsatellite primers developed for one species frequently amplify loci in related species.

"A major thrust of the Marine Gene Probe Laboratory (MGPL) has been the use of microsatellites to assist fish farms in selective breeding of aquacultural species. Highly polymorphic microsatellites (those with high allelic variability) allow the parents of superior progeny to be identified in mixed family rearing environments, thus enabling selective breeding to occur in commercial farms/hatcheries. No single alternative marker system could have served well in all of the applications described above." By 1994, microsatellite technology had been applied by MGPL for tracking relatedness and tagging for selective breeding in Atlantic salmon, rainbow trout, Atlantic cod, tilapia, carp, and scallop.

**Wright, J.M. and P. Bentzen. 1994./ Microsatellites: genetic markers for the future. Reviews in Fish Biology and Fisheries 4:384-388.