Genetic Diversity Study In Populations Of Scallop Chlamys Farreri And Argopecten Irradians And Molecular Phylogentic Study Of Several Bivalves In Pectinidae

DNA sequencing is very useful for the genetic diversity analysis at molecular level. Ribosomal internal transcribed spacer ITS-1 gene fragment of Scallop Chlamys farreri was amplified via polymerase chain reaction ( PCR ), the PCR products were ligated into T-vector, cloned and sequenced for 78 individuals, 3 populations of China (21 for Dalian, 20 for Qingdao and 18 for Changdao ) and one population of Republic of Korea. The length of ITS-1 gene fragment of Chlamys farreri was from 298bp to 304bp. The sequences were analyzed for its intraspecific genetic variation and geographic structure. 51 nucleotide positions were found variable, which included 13 deletions or insertions, 38 transitions and transvertions, and 46 haplotypes were detected in all samples. The genetic diversity indexes including S( polymorphic sites), P (nucleotide diversity) and K (average number of nucleotide difference) were calculated and results indicated that Korea population showed more variation than others and more differences to others, followed by Changdao and Qingdao population, and Dalian population had the least sequence diversity. However, parameters of genetic variation among the four populations indicated that little geographic structure were present. The data showed ITS-1 fragment was feasible as a marker tool for population genetic analysis. Our data provided baseline information at DNA level on the genetic variation in wild Scallop populations and may be useful for future management and utilization of the resource.Ribosomal internal transcribed spacer ITS-1 fragment of a cultured population of Scallop Argopecten irradians from Qingdao was amplified via polymerase chain reaction ( PCR ), the PCR products were ligated into T-vector, cloned and sequenced for 26 individuals, The aligned length of ITS-1 gene fragment of Argopecten irradians was 323bp. 12 nucleotide positions were found variable, which included 3 deletions or insertions, 9 transitions and transvertions, and 11 haplotypes were detected in all samples. The genetic diversity indexes including S( polymorphic sites), P (nucleotide diversity) and K ( average number of nucleotide difference ) were calculated and results indicated that the genetic diversity of Argopecten irradians cultured population was ina low level.The ribosomal transcribed spacer ITS-1 gene fragments of four species of scallops (Chlamys farreri, C.nobili, Argopecten irradians, Patinopecten yessoensis ) were amplified. The PCR products were ligated into T-vectors, cloned and sequenced. 337bp-360bp sequences obtained respectively. The sequences were aligned with the software Clustal , sequence length variations were not significant. There were two conservative regions among the sequences, their homogeneity was higher than 92%.The ribosomal transcribed spacer ITS-1 sequences we obtained from four species of scallops compared with the published gene sequences of four scallop species. The molecular data aligned with Neighbor-Joining, and Maximum-Parsimony methods, phylogenetic analysis showed that molecular trees by NJ and MP were consistent completely. Our result indicated that Argopecten irradians has a close relationship to subfamily Pectininae. The placement of C. nobili was closer to M.varia than to C. farreri which has a close relationship to P. yessoensis.