Objective In this study, the genetic diversity of the cultured Coreius heterodon population was analyzed by using the sequences of mitochondrial DNA Cyt b, 12S rRNA and displacement loop region (D-Loop), and the genetic diversity and genetic structure were preliminarily understood.
Methods PCR amplification and Sanger sequencing were performed using previously designed primers targeting the mitochondrial Cyt b, 12S rRNA, and D-Loop regions. The genetic diversity parameters were calculated by DNASP 6.12 software. The MEGA 11.0 software was used to analyze the base composition and variable sites of the DNA sequences. The genetic distances among haplotypes were calculated by the Kimura two-parameter model. The haplotype phylogenetic trees based on complete sequences of the mitochondrial DNA control region were constructed by neighbor-joining (NJ) method and the maximum likelihood (ML) method.
Results The sequences of mitochondrial DNA Cyt b, 12S rRNA, and D-loop used for analysis were 1 110−1 147 bp, 425−445 bp, and 972−1 023 bp, with average lengths 1 122.77, 430.00, and 1 000.47 bp, and median lengths of 1 122, 429, and 1 001 bp, respectively. A total of 8, 1, 14 variable sites, and 22, 19, 30 haplotypes were identified in the mitochondrial DNA Cyt b, 12S rRNA and D-loop, respectively, with genetic distance between haplotypes ranging from 0 to 0.004, 0 to 0.005, and 0 to 0.007, respectively. The average haplotype diversities based on mitochondrial DNA Cyt b, 12S rRNA, and D-loop were 0.547±0.010 5, 0.186±0.007 8, and 0.885±0.001 3, respectively; the average nucleotide diversities were 0.000 76, 0.000 44, and 0.002 58, respectively; and the average number of nucleotide differences was 0.830, 0.186, and 2.432, respectively. Mismatch-distribution showed a unimodal pattern, and Tajima’s D value was negative (D=−1.04, P>0.01) in the neutrality test, but the statistical result was not significant.
Conclusion The genetic diversity of the cultured C. heterodon population is relatively low, and there is extensive gene flow between haplotypes, with no genetic differentiation of the population, but the cultured C. heterodon population has undergone a population decline. Therefore, establishing a broodstock population with rich genetic diversity for artificial breeding of C. heterodon, solving the problem of broodstock cultivation, and continuously expanding the scale of C. heterodon farming population is the primary task.
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