Screening Of Highly Polymorphic EST-SSR Markers And Investigation Of Genetic Diversity In Macrobrachium Nipponensis

Oriental river prawn, Macrobrachium nipponense, is an important shrimp species in freshwater aquaculture. but the living marker is difficult because of the biological characteristics of Shelling. Molecular marker, as a genetic marker based on DNA polymorphism. it has been widely used in the analysis of genetic diversity; population and germplasm identification; genetic relationship research,correlation of related with properties marker screening. Microsatellites as the second generation of the molecular markers. because of it has the quality of good polymorphism, codominant inheritance characteristics, so it has been favored in genetics and breeding. so it is very necessary to screening valuable molecular markers that can be used in identify the germplasm resources. The Yellow River, the Yangtze River, the Pearl River as the three major rivers in china. The Oriental river prawn resources is abundant. Investigation and genetic analysis of the three populations are very important for resource protection and utilization of Macrobrachium nipponense.Through the searching of the Macrobrachium nipponense NCBI-EST Library （LIBEST₀27335of testis cDNA library; LIBEST₀23572of ovary cDNA Library） microsatellite sequence, primers were designed based on the obtained microsatellite sequences. Using Taihu wild shrimp group as a template for amplification, in accordance with the highly polymorphism information content index to measure the degree of genetic variation （PIC>0.5）,14pairs of EST-SSR markers were obtained, The average allele number was7per locus, ranging from4to13. The observed heterozygosity（Ho） ranged from0.4125to0.8938and the expected heterozygosity （He） ranged from0.6786to0.9332. The polymorphic information content （PIC） per locus varied from0.613to0.899.Using20microsatellite markers including the markers screened in this study and combined with the microsatellite markers were developed before, those20markers were used to analyze the genetic diversity of the three Macrobrachium nipponensis populations. The results show that:number of alleles （A） of the three shrimp populations were6.5500, 5.2500, and5.7000. The average polymorphism information content sites of twenty loci is0.7876. The observed heterozygosity of the three populations were0.4481,0.5013and0.4127; the expected heterozygosity of three populations were0.5210,0.5536,0.6529. it was showed that abundant of the three Macrobrachium nipponensis genetic diversity. From high to low of the expected heterozygosity was:the Pearl River, the Yangtze River, the Yellow River. Analysis of molecular variance （AMOVA） showed that, the majority of the variance in the three Macrobrachium nipponense was almost within populations （94.7%）, and5.3%was among populations. The Fst values between populations were0.0298to0.0552. The three groups of genetic similarity coefficient is0.8162to0.9143, the genetic distance was0.0193to0.1988. The genetic distance between the three groups in the0.0898-0.1530. The genetic distance between the Yellow River and the Pearl River is0.1530, the genetic distance between Pearl River and Yangtze River is0.0898. The genetic distance between the Yellow River and Yangtze Rive is0.1028.This paper screened the highly polymorphism of Macrobrachium nipponensis microsatellite loci, providing new molecular markers for Macrobrachium nipponensis. The Yellow River,Yangtze River, Pearl River, three major river shrimp resources were studied. Through the genetic diversity and genetic structure analysis, provide a reference for the protection exploitation and utilization of the wide Macrobrachium nipponense resources.