Study On The Genetic Diversity Of Oreochromisco Aureus

Tilapia,which is the main cultured species that the UN Food and Agriculture （FAO） recommendto the world, is also known as one of the main sources of animal proteins in the future. Tilapia industry has also become one of the most pillar industries of aquaculture in China. In this study, by using molecular biology, we analyzed the genetic diversity of Oreochromisco aureus, the following results will accelerate the development of tilapia industry.1.We made a research on the mtDNA D-loop of two Oreochromisco aureus, populations （A total of70individuals）, the size of the entire sequence was about1000bp.The number of mutation loci, haplotype diversity index, nucleotide diversity index, the average number of nucleotide differences of Nama were24,0.795,0.00176,1.640, respectively; and that of Wuming were respectively25,0.822,0.00191,1.788. Of70individuals,32kinds of haplotypes were found, and there were6kinds of Shared haplotypes, among those Hap₂4were most widely distributed. The phylogenetic tree of haplotypes showed that Oreochromisco aureus and Nile tilapia were firstly together as one, Then clustered into one with Sarotherodon melanotheron, Finally with Rainbow trout, Weeve, Plecoglossus altivelis, Carp and Zebrafish. These two geographic populations intertwined and showed no geographic differences, reflecting extensive gene flow and a certain genetic differentiation.2. A research on the mtDNA Col of two Oreochromisco aureus populations （A total of70individuals） indicated the size of the entire sequence was about1600bp.The number of mutation loci, haplotype diversity index, nucleotide diversity index, the average number of nucleotide differences of Nama were15,0.711,0.00057,0.911, respectively; and that of Wuming were respectively20,0.770,0.00075,1.197. Of70individuals,23kinds of haplotypes were found, and there were16kinds of Shared haplotypes, among which Hap₁were most widely distributed. The phylogenetic tree of haplotypes showed that Oreochromisco aureus and Nile tilapia were firstly together as one, then clustered into one with Sarotherodon melanotheron, it was consistent with the results of Nama. Two groups finally clustered into one with Weeve, Plecoglossus altivelis, Rainbow trout, Carp and Zebrafish. There were some differences between Col and D-loop.3. A research on the mtDNA Cytb of two Oreochromisco aureus populations （A total of70individuals） indicated the size of the entire sequence was about1200bp.The number of mutation loci, haplotype diversity index, nucleotide diversity index, the average number of nucleotide differences of Nama were12,0.494,0.00065,0.739, respectively; which was lower than that one in Wuming （respectively0.677,0.00090,1.022）. Of70individuals,14kinds of haplotypes were found, and there were10kinds of Shared haplotypes, among those Hap₂were most widely distributed. The phylogenetic tree of haplotypes showed that the relationship between Oreochromisco aureus and Nile tilapia and Sarotherodon melanotheronere was closer than the one between Carp and Zebrafish. There were some differences between CoI and D-loop. It was consistent with the results of D-loop and Col.4.Using20pairs of microsatellites, we investigated genetic diversity of Oreochromisco aureus from two important breeding centers, Guangxi Province. The results showed genetic diversity index of two Oreochrmisco aureus groups maintained a high level, which was consistent with Col, D-loop and CYTB. In addition, we found that artificial breeding would lead to the rise of genotype frequencies of superior economic traits and further homogeneity, enabling the level of genetic diversity decreased. There was a certain genetic differentiation in two groups of Oreochromisco aureus, strengthening its conservation breeding.In summary, we carried out some research about genetic diversity of tilapia, which reveals the level of genetic diversity. It will provide a scientific basis for future breeding of tilapia.