Mapping quantitative trait loci in European sea bass (Dicentrarchus labrax): The BASSMAP pilot study

There are great opportunities for genetic improvement in recently domesticated aquaculture species. However, the lack of appropriate tools limits the application of advanced techniques including the mapping of quantitative trait loci (QTL) and marker-assisted selection (MAS). The recent development of a genetic linkage map for the European sea bass allows the application of such methods for the first time in this species. We report a pilot trial of QTL mapping in a commercial sea bass population as a precursor to the application of MAS. Fertilized eggs collected on a single spawning day produced a population composed of a few large families. Fish were grown under commercial conditions, slaughtered at approximately 470 g and measurements were taken for several traits. Parentage analysis showed that the population consisted of 26 full sib families, with a common dam and several sires. Seven microsatellite markers spanning the largest linkage group (LG1) were then genotyped in 27 parents and their 422 progeny, in order to perform a QTL scan using half-sib interval mapping approaches. Significant QTL affecting six morphometric traits including length and depth, are reported. The success of the procedure demonstrates that QTL analysis can be applied in this species and will contribute to the study and future improvement of traits associated with production, profitability and sustainability.