Silver Carp Genetic Diversity From Four Famous Domestic Fishes Origin Field Revealed By Mitochondrial DNA D-loop Sequence

Hypophthalmichthys molitrix is one of the four famous domestic fish in China.It has a long-standing history in china aquaculture which is a commercially important fishery species and mostly distributed in the freshwater of china.In recent years,due to the construction of large-scale hydropower projects,the destruction of ecological environment,long-term overfishing,inappropriate artificial reproduction and proliferation and release,the fishery resources and germplasm resources of wild silver carp in China are sharply reduced.Therefore,it is very important to study the genetic diversity of parents and seedlings in artificial breeding and reproductive release.In this study,the D-loop sequences of mitochondrial DNA was used as a molecular marker to analyze the genetic diversity and genetic structure of the broodstocks and offspring of the Four Famous Domestic Fishes.The research results can provide the basis for the construction of the original stock farm of the Four Famous Domestic Fishes in China.We have sequenced and analyzed the mtDNA D-loop sequences of the broodstock and progeny of the Four Famous Domestic Fishes from Changsha,Jianli,Jiaxing,Ruichang,Shishou,Shaanxi,Wujiang and Yangzhou by the PCR technology.The main results as follow: First: analysis of genetic diversity and genetic structure of eight silver carp broodstocks(1)71 haplotypes were defined by the 303 individuals in eight silver carp populations.The average haplotype diversity Hd was 0.933±0.010,and the nucleotide diversity Pi was 0.016±0.001,which indicated that the genetic diversity of silver carp broodstocks in the original seed farm was high.(2)The total genetic differentiation index Fst of eight broodstocks of silver carp was 0.02181 and insignificant,indicating that the genetic differentiation of the eight populations was not significant.The AMOVA results showed that genetic variation within populations accounted for 97.82%,and genetic variation among eight populations only accounted for 2.18%.The results showed that genetic variation among eight populations mainly came from within species,and genetic differentiation among populations was insignificant.(3)The results of neutrality test and mismatch distribution of the eight populations showed that there had been no population expansion in the eight populations in recent years.The eight populations was relatively stable and had a long evolutionary history.Second: analysis of genetic diversity and genetic structure of eight silver carps progeny(1)37 haplotypes were defined by the 267 individuals in seven silver carp populations.The average haplotype diversity Hd and the nucleotide diversity Pi were 0.843±0.021,was 0.01506±0.00177,respectively,which indicated that the genetic diversity of silver carp progeny in the original seed farm was high.(2)The total genetic differentiation index Fst of the seven populations was 0.08037 and reached a significant standard,indicating that there were different degrees of genetic differentiation among the seven populations of the silver carps.The AMOVA results showed that the genetic variation within the population accounted for 91.96%.The contribution rate of variation was only 8.04%,it was significantly higher than that of the broodstocks population,it indicated that the main genetic variation of the seven populations still came from within the population,and the genetic differentiation among the populations was in low degree.(3)The results of neutrality test and mismatch distribution of the seven populations showed that there had no population expansion in the seven populations in recent years.The population was relatively stable.