Genetic Characteristics Of Sex Reversal And QTC Interaction Of Sex Determination In Half-smooth Tongue- Sole(Cynoglossus Semilaevis)

Half-smooth tongue-sole （Cynoglossus semilaevis Gunthers） is one kind of increasing-farmed fish varieties mainly distributed in the northern coastal of China. With fast growth, gentle, delicious smooth taste and high nutritional value of excellent features, adult half-smooth tongue-sole differs widely in size between males and females. mature females grow two to four times quicker rate than males, in addition, weigh is twice as much as males. Thus achieving high or full female breeding ratio in hale-smooth tongue-sole is important for improving breeding efficiency. However, due to the prevalent natural phenomenon of sex reversal, th males ratio accounts for a large part of population, individuals can not be discriminated in the early breeding, thus, male individuals will be difficult to fall into disuse, thus results in increased cost of breeding. Therefore, this article mainly goal is to reasearch sex reversal’s heredity characteristics’ mechanism, looking for the law of sex determination, aimed at providing reference information theory in fish sex control for breeding applications finally.The main study findings are shown below:（1）Adopted in accordance with sex linkage microsatellite marker primers designed by Chen et al. From 10 families’Fl generation of fresh blood to extracte genomic DNA for genetic sexing. primer expressed the 218bp,206bp two bands for females, only one expression of 218bp bands for males; the gonadal tissue sections were used for identifying biological sex. The results showed that genetic sex of females from 10 pedigrees have a lot of difference, up to 54% and the lowest was 21%; the proportion of male and female’s biological sex between different families also have significant differences, of which there are two families of all generations of female reversal for pseudo-male.（2） Using the logistic regression analysises the sex ratio between different families and split variance component within family and different families.Through calculating heritability of sex reversal, we found that the heritability of sex reversal is 0.058, so variability within the family should be considered including males and females when we choose a Gunther family with low sex reversal rate.（3） Taking sex as a binary trait, all bi-marker interactions are scanned with logistic regression model by utilizing high density microsatellite linkage map. Results show that 5 bi-marker combinations are detected at significance level of 0.05, among them, SCAFFOLD149₇459--SCAFFOLD7854₇1905 is significantly at 0.01 level.5 bi-marker combinations involve in 9 markers of 7 chromosomes. These detected markers are mainly located on chromosome 2,10 and 11, especially 2 bi-marker combinations located on linkage groups 10-11 and both have the marker of SCAFFOLD 149₇459 involved, which indicating that this marker may have a greater impact in the process of interaction. This study has shown that genes close to these markers are involved into sex determination of half-smooth tongue-sole. The results have important meaning for further study gender-related and sex control in half-smooth tongue-sole.