Objective In this study, the genetic diversity of the cultured population of Coreius heterodon 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 Using the specific primers designed by previous researchers based on the sequences of mitochondrial DNA Cyt b, 12S rRNA and D-Loop, polymerase chain reaction (PCR) amplification was carried out, and Sanger sequencing was performed. The genetic diversity parameters were calculated by the DNASP 6.12 software. The MEGA 11.0 software was used to count 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 of the 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, 12SRNA and D-loop, respectively, respectively, with genetic distance between haplotypes ranging from 0.000 to 0.004, 0.000 to 0.005 and 0.000 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 quantity 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.
DownLoad: