A Highly Redundant BAC Library of Atlantic salmon (Salmo salar): An Important Tool for Salmon Projects

Background: As farming of Atlantic salmon is growing as an aquaculture enterprise, the need to identify thegenomic mechanisms for specific traits is becoming more important in breeding and management of the animal.Traits of importance might be related to growth, disease resistance, food conversion efficiency, color or taste.To identify genomic regions responsible for specific traits, genomic large insert libraries have previously provento be of crucial importance. These large insert libraries can be screened using gene or genetic markers in orderto identify and map regions of interest. Furthermore, large-scale mapping can utilize highly redundant libraries ingenome projects, and hence provide valuable data on the genome structure.Results: Here we report the construction and characterization of a highly redundant bacterial artificialchromosome (BAC) library constructed from a Norwegian aquaculture strain male of Atlantic salmon (Salmosalar). The library consists of a total number of 305 557 clones, in which approximately 299 000 are recombinants.The average insert size of the library is 188 kbp, representing 18-fold genome coverage. High-density filters eachconsisting of 18 432 clones spotted in duplicates have been produced for hybridization screening, and are publiclyavailable [1]. To characterize the library, 15 expressed sequence tags (ESTs) derived overgos and 12 oligosequences derived from microsatellite markers were used in hybridization screening of the complete BAC library.Secondary hybridizations with individual probes were performed for the clones detected. The BACs positive forthe EST probes were fingerprinted and mapped into contigs, yielding an average of 3 contigs for each probe.Clones identified using genomic probes were PCR verified using microsatellite specific primers.Conclusion: Identification of genes and genomic regions of interest is greatly aided by the availability of theCHORI-214 Atlantic salmon BAC library. We have demonstrated the library's ability to identify specific genes andgenetic markers using hybridization, PCR and fingerprinting experiments. In addition, multiple fingerprintingcontigs indicated a pseudo-tetraploidity of the Atlantic salmon genome. The highly redundant CHORI-214 BAClibrary is expected to be an important resource for mapping and sequencing of the Atlantic salmon genome.