The Genetic Diversity Of Different Populations Of Trionyx Sinensis

Trionyx sinensis is one of the important special economic animals in China. In recent years, the aquaculture industry of Trionyx sinensis receives much concern because it's rich in nutrition, protein, delicious amino acids (glutamic acid and aspartic acid), unsaturated fatty acids, and some kinds of mineral elements, such as iron, zinc, chromium and so on. At present, China has successively established a number of stock seed farm, breeding farm in some provinces and cities, and starts conservation of germplasm resources and breeding of Trionyx sinensis. However the over twenty years of seed blind import and mismanagement, result in Trionyx sinensis germplasm mixture on a certain degree, and the restriction of the development of Trionyx sinensis farming. To ensure the long-term development of Trionyx sinensis farming industry, it's of great significance to detect and evaluate genetic diversity of Trionyx sinensis of different regions. And the analytical result can provide genetic background reference and theoretical knowledge for breeding work.We designed the primers to amplify the partial sequences of D-LOOP region which had faster evolutionary rate in mitochondrial DNA, and used SSCP combined with sequencing results, to analyze the genetic diversity of Trionyx sinensis different populations. Meanwhile, we also studied the genetic relationship between the hybrid's offspring (Japanese population♀×Yellow River population♂) and the parental offspring to investigate the impact of hybridization on genetic diversity of Trionyx sinensis from the molecular level. The results were as follows:(1) The variation and genetic diversity of mtDNA D-LOOP region partial sequences in three geographical populations of Trionyx sinensis was analyzed by PCR combined with DNA sequencing and SSCP techniques. The average contents of A+T (65.4%) were higher than that of G+C (34.6%). A total of 7 variable sites (about 5.7% of the total nucleotides in the sequence) were detected in 25 individuals, and the value of si/sv was 2.76. The nucleotide diversity (π) of the 25 individuals was 0.01995, and the average number of nucleotide differences (K) of them was 2.453. The 25 individuals belonged to 6 haplotypes according to the determined sequences. The haplotype diversity (Hd) was 0.707, and the average genetic distance (P) among the haplotypes of the species was 0.027. The analysis of phylogenetic tree with the method of UPGMA showed that the 6 haplotypes were clustered into three groups. Our data indicated that the variation and genetic diversity was high in the three populations of Trionyx sinensis, in which the genetic diversity of Japanese population was richer than that of Huanghe and Huangsha population, and the genetic distance between Huangsha population and the other two populations was far. Moreover, we found that two types of electrophoretic patterns could be detected by PCR-SSCP, and all typeⅡwere Japanese population, which suggesting the effective application of PCR-SSCP method in 78 T←�'A transversion mutation sites testing.(2) RAPD technology was used to analyze the genetic diversity of hybrid's offspring (Japanese population♀×Yellow River population♂) in Trionyx sinensis. Here, we used offspring of Japanese population, Yellow River population and Taihu population as a reference. The purpose of this study was to evaluate the impact of the hybridization on the T. sinensis germplasm, and provide reference data for the Breeding. 22 primers selected from 45 ones amplified a total of 176 bands ranging from 300bp to 2500bp, with an average of 8 bands gained per primer, of which 129 (73.30%) showed polymorphism in four populations. The order of proportion of polymorphic loci, Nei gene diversity index and Shannon information index: hybrid population> Japanese population> Yellow River population> Taihu population. The genetic similarity index of every two population ranged from 0.8351 to 0.9544 and the genetic distance ranged from 0.0467 to 0.1802 in 4 populations. The genetic distance between the offspring of hybrid and Yellow River population was the closest, and the genetic similarity between them was the greatest. These results showed: the genetic diversity of the four populations in T. sinensis was rich; hybridization events would aggravate the genetic diversity of hybrid offspring. These results would have some guidance for T. sinensis breeding.