Genealogical Identification, Effective Breeder Number Estimation And Correlation Analysis With Hereditary Characters Of Pinctada Martensii By Using SSR Marker

The pearl oyster Pinctada fucata is one of the main species to produce seawater pearl in china. The cultivation of seawater pearl has rapidly developed since the success of artificial breeding in1965. However, the quality of seawater pearl has decreased rapidly and relatively low price because of low growth rate and high mortality rate of the stocks. Consequently, genetic improvement of the stocks is urgent for pearl culturing.Thirty-six families were established by selecting mature breeders in the third generation selected line. In November2011, four families were randomly sampled from the thirty-six families and subjected to the experiment where genetic diversity and kinship of the sampled families were analyzed using thirteen microsatellite markers. Thirty-nine alleles were detected at thirteen microsatellite loci in the four families and the number of the alleles at each locus ranged from two to five. The average observed and expected heterozygosity of the four families varied from0.531to0.597and from0.474to0.507, respectively. The genetic differentiation index (Fst) among the four families was0.15. Based on the genotypes of offspring, all parental genotypes of the four families were successfully deduced. A dendrogram was constructed using UPGMA based on genetic similarity matrix. The UPGAM dendrogram of the120individuals indicated that98.3%of the individuals from each family could be fully clustered and the classification results were consistent with the source of genealogy. Results show that there exists highly genetic diversity among the four families and microsatellite marker is a useful tool for genealogical identification of pearl oyster.We choose90individuals from F4of Pinctada martensii randomly. Forty-five microsatellite markers were used to analyse genetic diversity of Pinctada martensii group and reconstruct of full-sibs relationships. Totally186alleles were detected at forty-five microsatellite locis in Pinctada martensii population and the number of the alleles at each loci ranged from2to9with a mean of4.13. The mean value of Hobs is from0.044 to1. The PIC value ranged from0.111to0.838. That showed these microsatellite locis have upper PIC. Shannon diversity index were between0.236and1.956. We succeed to deduce30full-sibs families on the basis of likelihood ratio algorithm of gene frequency. It means that75%parents take part in effective propagation. Inbreeding coefficient increment is0.83%between generations. The inbreeding coefficient of F4is3.27%. This research showed that this breeding group has a preferable genetic diversity and proved the method of reconstructing full-sibs relationships to calculate Pinctada martensii effective parent size by microsatellite markers is effectively. And it could avoid group inbreed when build next breeding system.In order to obtain growth traits linked microsatellite markers, the genome of the four generation selected line of pearl oyster Pinctada martensii was screened by50polymorphic EST-SSR, and then a correlation analysis between the markers and total weight, shell length, shell height and shell width of the selected line was performed by using a GLM model of SPSS software. Results showed that18loci were related to five phenotypic characters. We found that9loci were significantly correlated with body weight;12loci were significantly correlated with shell length;14loci were significantly correlated with shell height;6loci were significantly correlated with shell width;5loci were significantly correlated with ligament length. Favorable genotypes for each growth traits were obtained by a multiple comparison among the loci. In the present studies we obtained several growth traits linked microsatellite markers by a correlation analysis, which will help to design an effective molecular marker assisted breeding (MAS) in the species.