A new SNP-based vision of the genetics of sex determination in European sea bass (Dicentrarchus labrax).
BACKGROUND
European sea bass (Dicentrarchus labrax) is one of the most important farmed species in Mediterranean aquaculture. The observed sexual growth and maturity dimorphism in favour of females adds value towards deciphering the sex determination system of this species. Current knowledge indicates the existence of a polygenic sex determining determination system that interacts with temperature. This was explored by restriction-site associated DNA (RAD) marker analysis in a test panel of 175 offspring that originated from a factorial cross between two dams and four sires from a single full-sib family.


RESULTS
The first high-density single nucleotide polymorphism (SNP) based linkage map for sea bass was constructed, consisting of 6706 SNPs on 24 linkage groups. Indications for putative sex-determining QTL (quantitative trait loci) that were significant at the genome-wide threshold were detected on linkage groups 6, 11 and 18 to 21, although a genome-wide association study (GWAS) did not identify individual significant SNPs at a genome-wide threshold. A preliminary genomic prediction approach that tested the efficiency of SNP-based selection for female sea bass showed a slight advantage compared to traditional pedigree-based selection. However, when the same models were tested on the same animals for selection for greater length, a clear advantage of the SNP-based selection was observed.


CONCLUSIONS
Overall, the results of this study provide additional support to the polygenic sex determination hypothesis in sea bass. In addition, identification of sex-ratio QTL may provide new opportunities for sex-ratio control in sea bass.
Institute of Aquaculture, School of Natural Sciences, University of Stirling, Stirling, FK9 4LA, Scotland, UK. christos.palaiokostas@roslin.ed.ac.uk.|The Roslin Institute, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Midlothian, EH25 9RG, Scotland, UK. christos.palaiokostas@roslin.ed.ac.uk.
Christos
C
Palaiokostas
Institute of Aquaculture, School of Natural Sciences, University of Stirling, Stirling, FK9 4LA, Scotland, UK. michael.bekaert@stir.ac.uk.
Michaël
M
Bekaert
Institute of Aquaculture, School of Natural Sciences, University of Stirling, Stirling, FK9 4LA, Scotland, UK. j.b.taggart@stir.ac.uk.
John B
JB
Taggart
Edinburgh Genomics, Ashworth Laboratories, King's Buildings, University of Edinburgh, Edinburgh, EH9 3JT, Scotland, UK. Karim.Gharbi@ed.ac.uk.
Karim
K
Gharbi
Institute of Aquaculture, School of Natural Sciences, University of Stirling, Stirling, FK9 4LA, Scotland, UK. b.j.mcandrew@stir.ac.uk.
Brendan J
BJ
McAndrew
Ifremer, Chemin de Maguelone, F-34250, Palavas-les-Flots, France. Beatrice.Chatain@ifremer.fr.
Béatrice
B
Chatain
Institute of Aquaculture, School of Natural Sciences, University of Stirling, Stirling, FK9 4LA, Scotland, UK. d.j.penman@stir.ac.uk.
David J
DJ
Penman
Ifremer, Chemin de Maguelone, F-34250, Palavas-les-Flots, France. Marc.Vandeputte@jouy.inra.fr.|INRA, UMR1313 Génétique animale et Biologie intégrative, F-78350, Jouy-en-Josas, France. Marc.Vandeputte@jouy.inra.fr.
Marc
M
Vandeputte
D000818:Animals; D001492:Bass / Q000235:genetics*; D001947:Breeding; D005260:Female; D008040:Genetic Linkage; D008297:Male; D008957:Models, Genetic; D020641:Polymorphism, Single Nucleotide; D040641:Quantitative Trait Loci; D019849:Sex Determination Processes; D012744:Sex Ratio