Identification of two female-specific DNA markers in Verasper variegatus

Sex-specific DNA markers are powerful tools for genetic sex identification and sex control breeding of fish. Spotted halibut ( Verasper variegatus ) is a kind of marine flatfish with important nutritional and economic value, which exhibits significant sex-related growth dimorphism that the female individuals grow faster than the male individuals. However, there is no rapid, effective and universal sex-specific DNA marker used for genetic sex identification and sex control breeding in spotted halibut up to date. In the present study, whole genome resequencing was performed on 17 male and 17 female spotted halibut individuals to identify sex-specific markers. A total of 325.36 Gb and 328.99 Gb data were obtained from females and males, respectively. After reads mapping, sequencing depth and coverage analysis, 359 potential female-specific DNA sequences were identified. Then, after two rounds of verification, two female-specific 66 bp and 68 bp insertions were identified as female-specific markers which can accurately identify the genetic sex of spotted halibut through PCR amplification and 2% agarose gel electrophoresis. Subsequently, these two female-specific DNA markers and the PCR method were further validated using 117 spotted halibut individuals from another breeding population to confirm their genetic sex, which was in accordance with their phenotypic sex determined by histological section of the gonads. This may be the first two rapid, accurate and effective female-specific DNA markers used for genetic sex identification in spotted halibut. The identification of these two female-specific DNA markers will not only provide important genetic evidence to elucidate the sex determination mechanism of spotted halibut, but also help to advance the process of sex control breeding in spotted halibut.