Genetic diversity analysis of different geographic populations of black carp (Mylopharyngodon piceus) based on whole genome SNP markers

Black carp, Mylopharyngodon piceus, is one of the major farmed fish in China, generating a considerable amount of economic value annually. To investigate the genetic variation of black carp germplasm resources in China, this study was the first to use the whole genome SNPs of black carp for analysis. A total of 139 samples of nine black carp populations in the Yangtze River and Pearl River Systems of China were collected, and 53,322 high-quality SNP loci were obtained after GBS sequencing and filtering. Genetic diversity parameters were calculated for nine populations of black carp based on these genetic data. All 7 populations from the Yangtze River system and 2 populations from the Pearl River system showed high level of genetic diversity. For each population, the nucleotide diversity (pi) varied from 0.283 to 0.308, the observed heterozygosity (Ho) from 0.271 to 0.317, the expected heterozygosity (He) from 0.273 to 0.292,the number of effective alleles (Ne) from 1.440 to 1.475, and the polymorphism information content (PIC) from 0.224 to 0.239. The fixation index (Fst) between populations ranged from 0.036 to 0.133, remaining at low and medium differentiation. Phylogenetic tree analysis, principal component analysis (PCA) and population genetic structure analysis revealed that the nine populations could be divided into three ancestral populations. The seven populations of the Yangtze River system comprised two primary ancestral groups, with a small amount of gene flow between populations. The internal genetic structure of populations within the Pearl River system was homogeneous, with one common ancestral source as the dominant component. In conclusion, the data and results generated from this study will provide a useful addition to the genetic resources of black carp and will provide reference information for further germplasm conservation and genetic improvement of black carp.