| Aphi s glycines, Hemipter a, Aphididae, is an eating- leaves insect of cultivated soybean. It caused leaf cur l, shortened internodes, dwarf ing of plant height, even result in the death of the entir e plant, and directly caus ed the loss of seed production, lower the quality of oil, economic losses by sucking plant juices. It’s reasonable and important to clarify the genetic structure var iation and genetic divers ity of Aphis glycines populations hosting on soybean in China, to analyze it’s relative relationship between every geographic populations and to know the regular of demographic histor y in population expans ion are important to manage this pest.In this study, us ing two frequently-used mitochondr ial genes(mt DNA) COII and Cyt b, the populations of A. glycines hosting on soybean fr om 14 localities in China wer e studied and analysed by us ing a ser ies of bioinf ormatics methods, such as systematic phylogenetic analysis, genetic var iation and differ entiation analys is, and molecular biogr aphic geogr aph y analys is and so on. The main r esults of study were as follows :(1) Sequences of these two mtDNA genes( CO II, Cyt b)were obtained respectively by PCR from 627 individuals of A. glycines from 14 localities in China. The length of two mt DNA genes are 673 bp, 900 bp. Based on two gene sequences, 7 haplotypes of CO II gene, 13 haplotypes of CYT B wer e obs erved.(2) The CO II s equences and Cyt b sequences were analysed by DnaSP5.0. The r esults showed that base compos ition pr esent A/T bias is s imilar to the compos ition character of mitochondr ia, numbers of var iation is 12 and 20 respectively, the percentage of polymorphic s ites were 1.78% and 6.11% respectively; the values of haplotype divers ity(Hd) were 0.479 and 0.558 respectively; And the values of nucleic divers ity(Pi) were 0.00166 and 0.00107 respectively, suggested that ther e were no signif icant genetic diff erentiation and low genetic divers ity level occurred among populations. The Tajima’s D and Fu’s Fs test indicated that there might not have been a recen t population expans ion in its his tory of evolution, A. glycines populations are character ized by medium/low haplotype divers ity and nucleotide divers ity, resulting in no signif icant genetic differ entiation and Low genetic divers ity level occurred among pop ulations.(3) The two Neighbor- joining trees based on Kimur a 2-par ameter distances were constructed and used w ith A phis gossypii as outgroup, the r esult showed that all haplotypes into one and separ ated from the outgr oup. Haplotype networks wer e drawed with the median- joining method using Network 4. 1 softwar e. The results showed that the phylogenetic tr ees and haplotype networks did not r ef lect geogr aphic al pos ition, indicating a lack of obvious geographic structur e, and haplotypes were not c luster ed according to geographic population distr ibution.(4) AMOVA analys is based on tw o mt DNA genes haplotype frequenc ies us ing Ar lequin 3. 5. 1. 2 indicated that the genetic differ entiation of A. glycines populations in China occurred pr imar ily within populations( Genetic var iation w ithin population were 80.15%, 81.03% respectively), whereas the genetic var iation among populations was relatively low. The Nm for all groups was greater than one(Nm=2.019, Nm=2.135), suggesting that the level of gene f low among populations is not entirely deter mined by the migratory f light ability of insect.(5) Mantel test showed no s ignif ic ant linear dependence between genetic distance and geographic distance(R=0.1717, P >0.05), s uggesting that tempor ary r eproductive and geogr aphic isolation did not act as a barr ier for gene f low, and genetic var iation is not inf luenced by geographic distance. |
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