Screening and characterization of sex-linked DNA markers and marker-assisted selection in blue tilapia (Oreochromis aureus)

Abstract

The blue tilapia (Oreochromis aureus) is an important cultured fish worldwide, and exhibits sexual size dimorphism in favor of males, and therefore, mono-sex breeding is of great value for aquaculture. However, the lack of accurate sex-linked markers for blue tilapia has hampered the mono-sex culture in aquaculture, as well as study of sex determination in this species. In this study, WW super-females were bred and selected. Then, structure variations between WW and ZZ in sex determining region were identified from blue tilapia by comparative analysis of ZZ/ZW genome re-sequencing data from 5 different strains and ZZ/WW reference genome sequences. Based on these structure variations, 30 pairs of primers were designed to screen sex-linked markers. After two rounds of PCR screening, three markers, named as Marker-1, Marker-2 and Marker-3, were obtained to identify the genetic sex of blue tilapia. Marker-2 and Marker-3 were combined together for multiplex PCR amplification to distinguish ZZ, ZW and WW fish to make up for the lack of a co-dominant marker. In conclusion, three sex-linked markers were isolated and used for identification of different genotypes and establishment of MAS-GMT (marker-assisted selection of genetically male tilapias) technique in blue tilapia. It is also of great significance for isolation of sex determining gene, elucidation of the evolution of sex chromosomes and the transition of sex determination system.