Japan Expounds Different Geographic Population Genetic Diversity And Molecular Marker To Identify Research

Macrobrachium nipponense natively distribute in fresh water, and can be found in the most parts of China, Japan, Korea, Vietnam and Myanmar. In China, the resource quantity of this species is very abundant in lower and middle reaches of the Yangtze River, especially in the Taihu Lake. This species is a commercially important freshwater prawn species in China and Japan. But in recent years, the natural population genetics diversity and resource of M. nipponense have declined rapidly due to overfishing, degradation and fragmentation of its natural habitats. Studying the distribution of genetic diversity and genetic structure of wild population is important for developing conservation strategies.Inter-simple sequence repeat (ISSR) was used to detect the genetic diversity of two geographical populations of M. nipponense. The individuals of M. nipponense were collected from Changjiang and Taihu. Six primers, which were screened from all77ISSR primers, produced34polymorphic markers from two populations. The proportions of polymorphic loci of Changjiang and Taihu population were76.47%and73.53%, and Shannon’s index was0.3480and0.3465, respectively. These results showed that the genetic diversity index of the two populations were at the same level. Shannon’s index and AMOVA analysis indicated that genetic diversity mainly from individuals within populations. The UPGMA tree based on ISSR data supported this result and the distinct variation was detected. The results of ISSR analysis indicated that two populations of M. nipponense presented higher genetic diversity and there was a relatively normal level of genetic variation. There was some significant genetic differentiation between two populations.In this study, the amplified fragment length polymorphism (AFLP) was used to analyze the specific loci of the two populations (30samples for each) of M. nipponense from the Taihu Lake and the Yangtze River, respectively. A total of138loci were amplified with3pairs of primers. Normality test, homogeneity of variance test (F test) and significant difference between two samples mean test (t test) of loci frequencies were conducted. The statistical results showed that these two populations were different from each other indicating that they are two distinct and differentiated wild populations. χ2test was used to detect the differences between populations.The results showed that the frequencies of23loci were significantly higher in Taihu lake population than that of the population in Yangtze river (P<0.01), especially for loci BY160, BY320, BY470,BY520. These loci are population-specific loci for the Taihu Lake population. They can be used as specific markers to identify wild populations between from the Taihu Lake and the Yangtze River.As an important and useful polymorphic DNA marker, mitochondrial cytochrome oxidase subunit I(COI) gene was used to analyze the genetic diversity and genetic structure of four natural populations of M. nipponense, each of from the four freshwater lakes and rivers of Jiangsu Province, China, i.e. Taihu Lake(T), the Changjiang River(C), the Lixia River(L), the Hongze Lake(H). Total genomic DNA was extracted from the muscle of the10individuals from each of four populations. The result shows that thirty six variable nucleotide positions are detected in analyzed640bp COI sequences, and19haplotypes are defined among four populations, but only four shared haplotypes are observed. Each population has good haplotypic diversity and nucleotide diversity, and among them C and T shows the best genetic diversity. The Kimura2-paramter genetic distance calculated by the MEGA version3.1between the population of C and T is highest up to0.014, while that between the population of T and L is the lowest to0.002. This study chosen other species of Macrobrachium as out-group, and constructed the neighbor-joining(NJ) phylogenetic tree and the unweighted pair group method with arithmetic (UPGMA) phylogenetic tree based on the four populations of M.nipponense. The result shows that the population of C might have originated from one clade, while population of T, L and H might have originated from another.