Construction of a high-density microsatellite genetic linkage map and mapping of sexual and growth-related traits in half-smooth tongue sole (Cynoglossus semilaevis).

High-density genetic linkage maps of half-smooth tongue sole were developed with 1007 microsatellite markers, two SCAR markers and an F1 family containing 94. The female map was composed of 828 markers in 21 linkage groups, covering a total of 1447.3 cM, with an average interval 1.83 cM between markers. The male map consisted of 794 markers in 21 linkage groups, spanning 1497.5 cM, with an average interval of 1.96 cM. The female and male maps had 812 and 785 unique positions, respectively. The genome length of half-smooth tongue sole was estimated to be 1527.7 cM for the females and 1582.1 cM for the males. Based on estimations of the map lengths, the female and male maps covered 94.74 and 94.65% of the genome, respectively. The consensus map was composed of 1007 microsatellite markers and two SCAR markers in 21 linkage groups, covering a total of 1624 cM with an average interval of 1.67 cM. Furthermore, 159 sex-linked SSR markers were identified. Five sex-linked microsatellite markers were confirmed in their association with sex in a large number of individuals selected from different families. These sex-linked markers were mapped on the female map LG1f with zero recombination. Two QTLs that were identified for body weight, designated as We-1 and We-2, accounted for 26.39% and 10.60% of the phenotypic variation. Two QTLs for body width, designated Wi-1 and Wi-2, were mapped in LG4f and accounted for 14.33% and 12.83% of the phenotypic variation, respectively. Seven sex-related loci were mapped in LG1f, LG14f and LG1m by CIM, accounting for 12.5-25.2% of the trait variation. The results should prove to be very useful for improving growth traits using molecular MAS.