Genetic And Enhancement Effects Of Released Parent Grass Carp In The Middle Yangtze River

Grass carp Ctenopharyngodon idellus, as one of the four famous Chinese carps, is a commercially important fish species in China, and wild grass carp populations have been in serious decline because of Human factors and natural factors. For restoring grass carp resource, different measures have been adapted. And the enhancement has been mostly concerned, but the genetic impacts and enhancement-value of released parent grass carp on natural population are always doubted. In this study, two molecular markers (Microsatellite DNA and mitochondrial DNA) were used to evaluate the genetic effects comprehensively and accurately, and paternity tests were used to evaluate the effect of enhancement by microsatellite DNA marker. The main results were as following:1.13loci were used to evaluate the effect of enhancement. The composition of the three SSR mulitiplex-PCRs were optimized which could work preferably for different multiplex PCR, and three SSR mulitiplex-PCRs were developed. The results of paternity test revealed that contributions of released parent grass carp on natural grass carp offspring were7.6%and4.6%in2011and2012, respectively, and the exclusion probability was99.79%.2. All182specimens of four released parent grass carp populations and two natural offspring populations in2011and2012were studied based on mitochondrial Cytb and D-loop whole gene sequences. Results showed that65Polymorphic sites and22parsimony informative sites were in a2046bp gene sequences. And39different haplotypes were identified among182grass carp individuals. The average haplotype diversity (Hd) and the average Nucleotide diversity (π) of six populations were0.772and0.00100, respectively, and revealing a low genetic diversity and little differences among populations. The genetic differential index Fst of total six populations was0.01012, which meant that the genetic differentiation among six populations was low and significant (P>0.05) by Analysis of molecular variance (AMOVA). Mixed stock identification analyses estimated the proportion of two wild populations (ZBC^ZCC) in the mixed population at48.9145%and27.0545%, respectively. So there were almost no impacts on genetic diversity and genetic structure by released parent grass carps on natural offspring grass carp populations in this study.3. Four released parent grass carp populations and two natural offspring populations in2011and2012were studied based on microsatellite DNA marker. High levels of genetic diversity were determined in330Grass carp individuals with above0.8and0.7in heterozygosity and polymorphic information content in2011and2012, respectively. And significant differentiation among populations about group A and B was detected (Fis=-0.02315and0.01607, respectively), revealing no differentiation between populations. And this study was also proved that no impacts on genetic diversity and genetic structure by released parent grass carps on natural offspring grass carp populations.