Determination of Genetic Sex in Seriola ialandi ialandi Using Whole Genome Sequencing

Sex assignment is a critical issue in aquaculture for the development of broodstock populations. We used whole genome sequence of about 45 individuals in order to assess to what extent is possible to assign sex using differential haplotypes between sexes, for specific regions of the genome. Whole genome assembly of a single male and female were carried out, using different library preparations with an expected genome coverage of 50x. The data was mapped to either genome assembly in order to retrieve specific sex sequences based on the expected sex determination mechanisms (WW (male) WZ (female)) as observed for the Seriola genus. Several regions appear to be specific for the female assembly. We further perform GWAS as well as Fst analysis, based on the expected alleles distribution observed in each sex. A single region of about 2 kb harboring two haplotypes in close proximity, that can fully predict the sex of the broodfish. We developed an HRM protocol that accurately predicted the phenotypic sex observed in a broodstock population. Furthermore, these findings closely match histological data. Overall, we have found two haplotypes that can precisely predict the genetic sex in this species. This data is being incorporated in the current development of the Seriola array and will be an important step towards the development of this resource for aquaculture.