Study On The Genetic Diversity Of Different Groups Of Trichiurus Lepturus In The East China Sea

Trichiurus lepturus is the most important economic fish in the East China Sea,fishing production ranking the first place of a variety of economic fish perennially.In this study,to investigate the germplasm resources and generic diversity of T.lepturus,three populations(A,B and C)were collected to amplify the mitochondrial DNA 16 S rRNA and COI using PCR technique.To investigate the germplasm resources of T.lepturus collected from Zhoushan fishing ground-ZS(122°32’E 29°55’N),Wentai fishing ground-WT(124°24’E 27°26’N),Yuwai fishing ground-YW(125°47’E 29°44’N),Mindong Fishing Ground-MD(122°54’E 26°41’N),SNP loci and polymorphism analysis based on mt DNA COI gene were carried out using direct sequencing technique.The main results were as follows:1.Three populations were collected to amplify the mt DNA gene COI and 16 S rRNA,obtaining the length of 1130 bp(COI gene)and 554 bp(16S rRNA gene).T,C,A,G and A+T base content of COI gene sequences were 29.0%,28.9%,24.4%,17.7% and 53.4%,while T,C,A,G and A+T in 16 S rRNA gene sequences were 22.7%,27.6%,28.0%,21.7% and 50.7% respectively.The content of A+T was higher than C+G generally,which was match with the other teleost mitochondrial DNA and the bases combination characters of COI and 16 S rRNA gene sequences.Forty-three haplotypes,49 polymotphic sites and 6 conversion/subversion rates were detected in COI gene sequences while eight haplotypes,eight polymotphic sites and seven conversion/subversion rates were detected in 16 S rRNA gene sequences,which neither of them had been in saturation state.The COI gene sequences were more diversified and various than 16 S rRNA.The Neighbor-Joining(NJ)phylogenetic trees using adjacent method showed that many individuals in the same group can make the aggregation,but the aggregation of individual T.lepturus from different groups also happened.The results indicated that high frequency in gene exchange among groups led to low generic differentiation.Population A gains richer generic background than that of B and C.The difference among individuals within group was higher than the difference among different groups.The three populations of T.lepturus were in low generic diversity based on mt DNA 16 S rRNA and COI gene.2.Ten SNP loci were screened based on the sequence alignment of mt DNA D-loop and the COI gene.The results showed that the observed range of heterozygosity(Ho)was 0.0625~0.2812 and the distribution of heterozygosity(He)was 0.1190~0.3989(P<0.01).One locus(Tl-10)was deviated significantly from the Harding-Weinberg equilibrium(HWE)(P<0.05).The polymorphism information content(PIC)of two loci(Tl-08,Tl-09)were 0.2713 and 0.3140,respectively,belonging to moderate polymorphism(PIC<0.5),and six loci(Tl-01,Tl-02,Tl-03,Tl-05,Tl-06 and Tl-07 loci)were between 0.1103 and 0.2125.