Characterization, Genetic Linkage Mapping Of Microsatellite Markers In The Black Rock Fish (Sebastes Schlegelii)

The black rockfish, Sebastes schlegelii, is a valuable marine fish in China. It isovoviviparous fish which mate in the autumn and give rise to fry in the following May.In this study, the microsatellite markers were isolated for the rock fish (S. schlegeli)through construction of microsatellite enrichment libraries and colony hybridization.A total of1073positive clones were screened and sequenced. Of the809successfullysequenced clones,982microsatellite sequences were identified in770positive clones,which accounted for95%clones sequenced. A total of518microsatellite loci wereselected for primer design and for detection of polymorphisms, of which307pairs ofprimers provided clear amplification of polymorphic products in6randomly selectedwild individuals. The polymorphic loci accounted for52.84%of all microsatellitesequences detected. From polymorphic loci38were characterized in30wildindividuals. The number of alleles ranged from2to8, averaged5per locus. Theobserved heterozygosity (HO) and expected heterozygosity (HE) ranged from0.2414to0.7931and0.2250to0.8185, respectively. The polymorphism information contents(PIC) ranged from0.1760to0.8143, and averaged0.5704. The result showed that thewild rock fish (S. schlegeli) still has relatively high population genetic diversity.The microsatellite has been used in individual and parentage identification ofaquatic animals. In this study we analyzed4maternal families using17highlypolymorphic microsatellite loci. The result showed that in family#1the number ofpaternally derived alleles amplified by each locus was1to2, in family#2the numberpaternal alleles was2to5, while in family#3and#4the number paternal alleles was2to4. Locus had generated more than6paternal alleles was not found. From theseresults we conclude that family#1was full-sib family derived from one male, family #3and#4were half-sib family produced by the mother mating with two males, whilefamily#2was maternal family that contributed by at least three males. These resultscan provide important support for the construction of genetic map.Using family#1identified above as mapping population, the genetic linkage mapof the black rock fish was constructed with221polymorphic markers. Of the159markers used in female,144markers were successfully mapped to the female linkagemap including27(18.75%) markers showing significant segregation distortion. Thefinal female linkage map consisted of25linkage groups spanning1130.7cM, with anaverage distance of10.8cM. For male map,176markers were used and162markerswere assigned to26linkage groups including29(17.9%) markers showingsignificant segregation distortion. The total length of the male map was1137.0cM,with an average distance of9.6cM. The integrated genetic linkage map wasconstructed using202markers, among of which183markers were assigned to26linkage groups. Totally32(17.49%) markers showing significant distortion wereincluded. The whole linkage map was1200.3cM, with an average distance of8.5cM.The estimated genome length was1668.1cM for female and1627.2cM for male.Therefore coverage of the linkage maps constructed for female and male was67.8%and69.9%respectively. The average estimate length of integrated genetic linkagemap was1636.5cM, so the coverage of the present map was73.7%.The method of family identification and first genetic linkage map of the rock fish(S. schlegelii) constructed in this work would be very useful for improving molecularmarker-assisted selection, estimation of heritabilities of economic traits based onfamily construction.