The Genetics of Muscle Color in Atlantic Salmon

The highly appreciated and characteristic red muscle color of many salmonids is the results of astaxanthin deposition in the muscle. In farmed Atlantic salmon (Salmo salar), fillet redness is primarily affected by the dietary amount of astaxanthin, but also the genetic background and fish health appear to affect the color. If injected intraperitoneally, Atlantic salmon may achieve similar amounts of muscular astaxanthin as salmonids in the Oncorhynchus lineage. Thus, there is a bottleneck in the astaxanthin metabolism working against achieving a more intensely red colored Atlantic salmon muscle. As recent observations on fillet color show a declining trend, improving muscle redness through use of molecular genetics has the potential to improve product quality without increasing dietary astaxanthin levels. We measured fillet color in 6,440 Atlantic salmon derived from four year classes, and genotyped the same animals using AquaGen’s 220k- and 50k SNP-chips. GWAS identified three major QTL, all of which were highly significant in all year classes. When combined, the QTLs have the potential to improve muscle redness with up to 50%. Fine mapping of the region surrounding the highest scoring SNPs resulted in the identification of putative candidate genes and putative causative mutations for carotenoid metabolism in Atlantic salmon. The QTLs are being used for marker-assisted selection within the AquaGen breeding nucleus as well as for “niche” production of salmon eggs for customers putting particular emphasis on fillet color.