| The codling moth Cydia pomonella (L.) is a destructive fruit pest in fruit orchard, whicha host of host plants include apple, pear, peach, cherry, apricot and walnut, etc. Currently, thecodling moth is ubiquitous in the worldwide apple growing areas, and causes enormouseconomical loss in the entire fruit industry. In1957, the codling moth was first reported inXinjiang. It has now been spread throughout Xinjiang, Hexi Corridor in Gansu, Zhongweicity of Ningxia, Alxa of Inner Mongolia and southeastern Heilongjiang.In this study, we investigated the population genetics of20codling moth populationsfrom the invasive areas (Xinjiang, Gansu and Heilongjiang) in China and9foreignpopulations (Austria, Byelorussia, Germany, Italy, Israel, South Africa, Switzerland, UnitedKingdom and America) based on3mitochondrial DNA genes. Nucleotides composition,variable sites, nucleotide diversity and haplotype diversity of29codling moth populationswere analyzed. The population genetic diversity of the codling moth introduced into thedifferential regions in China explored the reasons caused the variability of the geneticdiversity and genetic differentiation. Additionally, the haplotype information discussed theorigin of the disparate populations. Furthermore, the results had a constructive guidingsignificance for the intergreted pest management of the coding moth under the currentcircumstances. The results and conclusions are as follows:1.483individuals from20Chinese populations and9foreign populations wereamplified and sequenced for the three mitochondrial genes (COI, COII, Cytb).435bp COIfragment length amplified and contained27variable sites,18of which were parsimonyinformation sites, and9were singleton sites.660bp fragment from COII sequence had43variable sites,31of which were parsimony information sites, and12were singleton sites. AndCytb fragment amplified710bp and found54variable sites,30were parsimony sites and24were singleton sites. It indicated no insertion or deletion found in all sequences. Theproportion of variable sites was6.2%(COI),6.3%(COII) and7.6%(Cytb), respectively.Additionally, three genes displayed base bias which A+T contents were considerably higherthan G+C contents that was according with insect mitochondrial DNA nucleotide composition.2. There were142haplotypes of three mitochondrial genes obtained in29populations, including42,44, and56haplotypes in the mtDNA COI, COII, and Cytb, separately. Analysisdate showed that13haplotypes in COI were shared in all populations,16haplotypes wereshared in COII sequences, and13haplotypes were shared in Cytb sequences. At the sametime, haplotype H11in COI gene contained169individuals of21populations, while H3inCOI hold48individuals of9populations. Haplotype H2in COII had172individuals of22populations, while H7in COII contained45individuals of15populations. Haplotype H5inCytb was distributed in153individuals of22populations. Furthermore, the distribution ofhaplotype in populations was disequilibrium. The haplotypes found at high frequency teded tobe ancestor haplotypes.3. The haplotype diversity and nucleotide diversity of COI gene was0.824and0.00794,while COII gene was0.822and0.00541. Likewise, the haplotype diversity and nucleotidediversity of Cytb gene was0.814and0.00615. The results indicated relatively high geneticdiversity in codling moth populations. The haplotype diversity of foreign populations was0.862-0.909, while the range of nucleotide diversity was from0.00810to0.01021. Thehaplotype diversity of Heilongjiang populations was from0.762to0.896, while the extent ofnucleotide diversity was between0.00448and0.00583. The haplotype diversity of Xinjiangpopulations was from0.441to0.693, while the range of nucleotide diversity was between0.00105and0.00473. Furthermore, the haplotype diversity of Gansu populations was from0.549to0.684, as the range of nucleotide diversity was between0.00203and0.00668.Consequently, the result clearly manifestoed that foreign populations had comparativelyhigher genetic diversity than Heilongjiang populations however the genentic diversity ofXinjiang and Gansu populations was at a low level. It presumed founder effect in Xinjiangand Gansu populations during invasion process. Higher genetic diversity in Heilongjiang maybe caused by shorter invasion history and multiply introductions.4. Analysis of haplotype phylogenetic tree demonstrated haplotypes divided into twoclades (A and B) in three mitochondrial genes. However, there was no obvious geographicalpattern for the prevalence and distribution of the haplotypes. In contrast to the strong splittingin two major clades, the resolution between the single haplotype within each of the two cladesis rather weak. Alternatively, the whole domestic haplotypes were distributed in clade A,besides one haplotype of MDJ population in clade B.5. The AMOVA results suggested significant genetic differentiation at three hierarchieswhich were grouped according to the sampled regions including Xinjiang, Gansu,Heilongjiang and foreign. Human-aided dispersal has a vital influence on geneticdifferentiation, yet, the weak flight capacity limitted gene flow between populations whichboost the differentiation of geographic populations. 6. Analysis of haplotypes composition displayed seven haplotypes (H1, H2, H3, H4, H8,H11) in COI gene, six haplotypes (H2, H7, H8, H13, H14, H22) in COII gene and fivehaplotypes (H5, H12, H17, H24, H29) in Cytb gene were shared between European andChinese populations. The data revealed that Europe was the invasion source of Chinesecodling moth. There were4haplotypes (H2, H4, H11, H35) in COI gene, three haplotypes(H2, H7, H40) in COII gene and three haplotypes (H5, H45, H47) in Cytb gene of Gansupopulations shared with Xinjiang populations, which indicated codling moth to Gansu fromXinjiang. Three haplotypes (H29, H30, H31) in COI gene and four haplotypes (H29, H30,H32, H33) in COII gene of Heilongjiang populations was shared between Heilongjiangpopulations. Moreover, certain special haplotypes only showed in Heilongjiang populations.So we deduced that Heilongjiang populations may be multiply introductions. |
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