Genetic Diversity Of MtDNA D-loop Region And Microsatellite DNA Of Silver Carp (Hypophthalmichthys Molitrix)

Silver carp(Hypophthalmichthys molitrix) has been one of the most important traditional domestic, commercially valuable and important freshwater aquaculture fish in China. As the violent changes in environment of Yangtze River drainage in recent years, the output of silver carp in Yangtze River has declined sharply. Because the management of genetic resources and the use method were imperfect, the performance of growth has decreased, the resistance of sickness has reduced obviously and the genetic diversity has turned lower. The national level Tianjin Huanxin high quality fish farm (in Ninghe county) had been selecting six generations of silver carp over 40 years, the original silver carps were 1000 individuals collected from Yangtze River at 1957, F6 was called "Jinlian" in 2001 and The Jinlian was identified a "new breed" by National committee of original species and breed in aquiculture in 2010. In this study, silver carp populations from Yangtze River drainage and the artificially propagated population were investigated using PCR-RFLP of the mtDNA D-loop region and microsatellite DNA markers. The results of the investigation are not only useful for protecting and taking advantage of germplasm resources, but also the support of the theoretical basis data of silver carp.1. The restriction fragment length polymorphisms of the mtDNA D-loop region of 158 individuals of silver carp were analyzed with PCR technique. The wild samples were collected from Yangtze River drainage area (Jianli section in Hubei Province. Ruichang section in Jiangxi Province and Changsha section in Hunan Province) respectively. The artificially propagated population was the Jinlian (sixth generation). The D-loop regions amplified were digested with 14 restriction endonucleases. The results showed that the length of the DNA fragments amplified in all samples were about 1.6 kb. The restriction sites were observed with 10 enzymes (Afaâ… . Aluâ… . Draâ… , EcoRâ… , Haeâ…¢, Hapâ…¡, Hinfâ… , Mboâ… . Taqâ… and Xspâ… ) and 16 haplotypes were detected. Haplotype I occupied 57.5%-90.0% in four populations. The haplotype diversity (h) and nucleotide diversity (Ï€) in four populations were 0.1885-0.6526 and 0.001182-0.007570. The Rogers'genetic distance between Jianli and Ruichang populations was the shortest (0.1250) while it was the farthest between Jianli and Ninghe (0.2693). The x2 test showed that there was significant variance among four populations. The haplotype diversity (h) and nucleotide diversity (Ï€) in Ninghe population were both the highest and pattern C of Hinf I was unique in Ninghe population, occupying 20%.2. The seven pairs of microsatellate markers were used in the analysis of 88 individuals from Ruichang and Ninghe populations of silver carp with PCR technique. In Ruichang and Ninghe populations, the number of ailele in every locus was 2-6 and 3-7; the number of allele per locus was 4.1429 and 4.5741; the average number of effective allele was 2.4030 and 2.5026; the value of average observed heterozygosity was 0.5464 and 0.4977; the value of average expected heterozygosity was 0.5060 and 0.5191; the average PIC was 0.4503 and 0.4773. The 34 alleles were detected in seven loci; the 27 alleles were mutual in two populations. Seven loci were all polymorphic. The genetic similarity coefficient between two populations was 0.9560, the Nei's genetic distance was 0.0450 and the value of Fst was 0.0209 respectively. Ruichang and Ninghe population were moderately differentiated, the genetic distance between two populations was close, the genetic differentiation was not obvious.