Studies On The Molecular Genetic Markers And Their Applications In The Scallop Of Chlamys Farreri

RAPD (Random amplified polymorphic DNA) technique was used to study the genetic structure and genetic differentiation of the natural population and the hatchery stock of Chlamys farreri. Amplifications with 20 10-base primers under predetermined optimal reaction yielded 153 reproducible amplified fragments ranging from 200 to 3000bp. The mean proportions of polymorphic amplified fragments of natural population and the hatchery stock were 73.2% and 70.6% respectively, and the mean hetreozygosities of them were 0.27 and 0.26 respectively. The inbreeding index and genetic distance based on the gene frequencies were 0.0283 and 0.028. The higher values of heterozygosity and proportions of polymorphic loci of the natural population indicated that the natural resource of C. farreri in China was in good condition with higher genetic diversity. It is urgent to establish the effective measures to protect the resource. The hetreozygosity and proportion of polymorphic loci of hatchery stock were lower than that of the natural population, which could be related to the small size of the cultured stock and the higher possibility of inbreeding. The approaches such as Marker-Assisted Selection (MAS) should be induced into the scallop culture industry to ensure the sustainable development of the industry.Crossbreeding of Chlamys farreri were performed using the parent scallops from the Korea wild population (K), China cultured stock (C) and the survived individuals in epedimic waters in culture area of China (Cs). Four crosses, K×K, K×C, K×Cs and C×C, were constructed. The index of growth performance of their progenies such as the length and width of the shell and the individual weight were measured for heterosis study. Population genetic structure was studied using RAPD analysis to reveal the relationship between the genetic variations and heterosis. The index of growth performance of hybrids K×C were better than their parents, which indicated that heterosis existed between different populations of C. farreri. RAPD analysis revealed that the genetic distance between Korea wild population and China cultured stock, and the stock of survived individuals in China epedimic waters were 0.0036 to 0.0057. The mean expectedhetrozygosity of the above populations were 0.283, 0.267, 0.268, and 0.266,respectively； the proportion of polymorphic loci were 0.765, 0.760, 0.760 and 0.735, respectively,and the inbreeding index based on the gene frequencies between Korea wild population and China culture stock was 0.0508. The results indicated that the genetic differentiation occurred between the different geographic populations of C. farreri and the heterosis was related to the genetic distences of populations. The cDNA liberary of C. farreri was constructed and 6935 ESTs were generated. Of these ESTs sequences, 42 microsatellite-containing sequences were found by using the on-line bioinformatics software RepeatMasker. 7 pairs of microsatellite primer were designed based on the microsatellite-containing sequences. 6 primers worked in the wild populations from China, Japan and Korea, and 3 pairs of primer yield polymorphic products that could be used in the study of population genetics and mapping. The result indicated that there were microsatellite loci in the expressed sequences and ESTs analysis could provide a new approach to find microsatellite markers in scallop.