Screening and characterization of sex-linked DNA markers in Mozambique tilapia (Oreochromis mossambicus)

The Mozambique tilapia (Oreochromis mossambicus) is an important aquaculture fish. It shows sexual dimorphism in growth, with males growing much faster than females. Thus, production of all-male fingerlings of Mozambique tilapia would improve aquaculture efficiency. However, the lack of accurate sex-specific markers has hampered the mono-sex breeding and the study of the molecular mechanisms of sex determination in this species. Recently, we performed genome sequencing and re-sequencing of female and male Mozambique tilapia and identified the sex chromosome and sex determining region. In the present study, two sex-linked SNP markers were identified and validated. Male specific contigs were assembled from the unmapped reads after aligning male re-sequencing data against the published XX genome. Based on these male-specific contigs, three sex-linked DNA markers, Marker-1, Marker-2 and Marker-3, were developed and correctly identified the genetic sex of 16 fish. The universality of these three male-specific markers was then tested in a panel of 144 individuals, which showed a discrepancy of 5.5% (8/144) between genotypic sex and phenotypic sex. In conclusion, we developed three sexlinked markers to identify different sex genotypes in Mozambique tilapia. This study lays a foundation for the establishment of MAS-GMT (marker-assisted selection of genetically male tilapias) technique and sex-controlled breeding of Mozambique tilapia, as well as for the identification of the sex determining gene.