| Thysanoptera insects commonly called thrips, among of these thrips species1%are crop pests,causing great influence on growing crops and harvestable products. In recent years, with the increasingof international trade activities, biological invasion events occurred frequently, invasive thrips speciessuch as Thrips palmi or Frankliniella occidentalis, has become the dominant pest in many of the regionsit has invaded. Thrips are a species-rich order, their small size, cryptic behavior and easily spreadingwith fruits, vegetables, flowers and nursery stocks, makes them difficult to be identified quickly and ac-curately. In the present study, DNA barcoding technology has been developed to identify common thripsspecies, and then establish the thrips barcoding system, and analyze different geographical population ofF. occidentalis in China. The results are significant for preventing thrips pests further invasion andspread, protecting the country trade credit and agriculture and forestry production safety. The main re-sults are as follows.(1) Application of DNA barcoding technology for species identification of common thrips. In thisstudy, the mitochondrial cytochrome c oxidase subunit I (COI) genes of27thrips species common inChina were amplified using DNA barcoding universal primers. The obtained partial COI fragments(about650bp) were sequenced. The phylogenetic tree was established by a neighbor-joining (NJ)method. The intra-and inter-species genetic distances were calculated with MEGA version4.0software using the Kimura2-Parameter model. The results indicated that the identification resultsbased on the phylogenetic tree obtained were consistent with those based on morphological characteris-tics for the27thrips species. In these species, the lengths of intra-species branches were much shorterthan those of the inter-species branches. Each branch corresponded to one species and all bootstrap val-ues of the original divergence among different haplotypes within a same species were100%. The geneticdistance between species in these27species was101.0times higher than the corresponding valueswithin species (0.2726vs.0.0027). There was no overlap between inter-and intra-species genetic dis-tances. The results suggest that the DNA barcoding based on partial COI gene can provide rapid and ac-curate identification of these thrips species.(2) The establishment of thrips barcoding system. The database mainly includes the specimen data-base, the knowledge database and barcoding sequence database. The specimen database contains samplecollecting information and DNA samples, sample collecting information including sample coding, host,collecting location, latitude and longitude, the DNA samples stroed-80oC. The sample collecting infor-mation of29common thrips species and360DNA samples were recorded in the specimen database.Knowledge database contains the species name, Latin name, distribution, morphological characteristics,host plant, biological characteristics, prevention and treatment measures and so on, the knowledge in-formation of29common thrips species were recorded in the knowledge database. A total of1671COIsequence of133thrips species were recorded in the barcoding sequence database, these sequences on theone hand from the laboratory obtained (387sequences in3families,13genus,29species), on the other hand from BOLD (541sequences in3families,22genus,80species)and NCBI (743sequences in3families,22genus,73species). The function of barcoding system contains COI sequence identification,sequence inquires, sequence submitting, my sequence management and so on. The barcoding system canidentify133thrips species, which is of great significance in realizing the remote recognition and effec-tive monitoring of invasive pest.(3) Spread trending analyse of F. occidentalis in main distributions of China. In this study, the COIgenes of175samples from13location sites were amplified to reveal the genetic diversity and geneticdifferentiation of F. occidentalis from different geographical population. All175sequences were ana-lyzed, defining13haplotypes, the haplotype diversity (Hd=0.691) was quite higher than nucleotidediversity (π=0.00652). Regarded all the populations as a whole, the Fst value was0.24359and the Nmvalue was0.78. The Fst and Nm value among populations showed that different geographic populationshave emerged certain differentiation. The results of AMOVA suggested that genetic differences mainlyoriginate from inter-population differences, with relative little genetic variation within populations. Thephylogenetic tree obtained different haplotypes from domestic and foreign geographic populationsshowed that F. occidentalis in main distributions of China existed two strains, the greenhouse strain andthe lupin strain. The lupin strain mainly came from New Zealand and Netherland, while the greenhousestrain had more than one invasion sources. In China, F. occidentalis was first intercepted and captured inYunan in2000, but it wasn’t reported as an invasive species until2003when it was discovered in agreenhouse in Beijing, we inferred the invasive source of F. occidentalis from different gepgraphic pop-ulations, on the one hand, may be in the process of international trade, introduced into China fromabroad, on the other hand may be in the dispatching process of the domestic, spreaded to other areasfrom Beijing and Yunan. The results are significant for preventing pest thrips further invasion andspreading in China.In this study, the research of molecular identification technology of thrips species and genetic di-versity and structure analyse of F. occidentalis from different geographical population, has great signifi-cance in port quarantine, preventing the introduction and spread, monitoring population expand and ex-ploring invasion mechanism. The establishment of thrips barcoding system has important impact onproviding technical support for the remote recognition and monitoring of invasive F. occidentalis andother invasive pests and protecting the country trade credit and agriculture and forestry production safe-ty. |
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