Genetic diversity of common carp (Cyprinus carpio L.) in Vietnam using four microsatellite loci

Four highly variable microsatellite loci were used to investigate genetic diversity and population structure of common carp in Vietnam. A total of 968 fish were genotyped representing three groups comprising: three experimental lines from the Research Institute for Aquaculture No 1 (Bac Ninh); 11 hatcheries; and six wild populations from rivers and reservoirs giving 72 alleles over all loci. The mean number of alleles, per locus per population ranges from 4.25 to 11.00 and the mean observed heterozygosity at the four loci ranges from 0.40 to 0.83. An analysis of the distribution of genetic variation indicated within population variation is very high (90.6%), while among populations within groups and among groups is low (5.0% and 4.5% respectively). Highly significant deviations from Hardy-Weinberg, mostly due to deficits of heterozygotes, were found in both experimental and hatchery groups suggesting either inbreeding or recent stock mixing. Wild common carp populations exhibited more genetic diversity than cultured populations in term of allele richness and observed heterozygosity. Results from assignment tests for the 20 populations of carp indicated that the experimental common carp lines can be largely distinguish from one another and that mixing between indigenous and introduces carp is occurring in hatcheries and possibly also in wild populations. Multidimensional Scaling (MDS) and UPGMA analyses show that the experimental Vietnamese white carp line is closely related to wild common carp populations; the hatchery stocks are mostly closely related to the experimental Indonesian yellow carp line but with evidence of some mixing; and the domesticated Hungarian population is highly divergent and not closely related to any other carp populations.