Identification of single nucleotide polymorphisms in candidate genes for growth and reproduction in a nonmodel organism; the Atlantic cod, Gadus morhua.

Recent technological developments have facilitated intensified searches for genetic markers under selection in nonmodel species. Here, we present an approach for the identification of candidate gene variation in nonmodel organisms. We report on the characterization of 82 single nucleotide polymorphisms (SNPs) and on the development of a specific genotyping assay for 30 SNPs in 18 candidate genes for growth and reproduction in Atlantic cod (Gadus morhua). These markers can be used for scanning natural populations for signatures of selection in both contemporary and archived historical samples, for example in retrospective studies assessing the effects of environmental changes, such as increasing temperatures, and selection imposed by high fishing pressure. Furthermore, these gene markers may be of interest to aquaculture, serving as a starting point for linking phenotypic traits important for productivity with genotypes and potentially be of use for marker-assisted selection in the future. This study demonstrates that the candidate gene approach is a valuable and targeted complement to the more random approach for discovering genetic variation in the genome and transcriptome applied through high throughput methods in nonmodel species.