Dissertation > Agricultural Sciences > Plant Protection > Pest and Disease Control > Plant pest and its control

Survey in Nanjing and Analysis of the Mitochondrial Genome of Frankliniella Occidentalis (Pergande)

Author YanDanZuo
Tutor FanJiaQin;LiuXianJin
School Nanjing Agricultural College
Course Agricultural Entomology and Pest Control
Keywords Frankliniella occidentalis Nanjing electron scanning microscope PCR identification Mitochondrial genome Sequence analysis
CLC S433
Type Master's thesis
Year 2011
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Western flower thrips Frankliniella occidentalis(Pergande), firstly found in Beijing in the mainland of China, in 2003, is a cosmopolitan agricultural pest and one of the most important quarantine pests in the world. The host plant range survey of flower thrips was took among 54 plant varieties in Nanjing, by checking the thrips collected from the flowers of the plants through optical and scanning electron microscope. Primers designed based on the COI gene of mtDNA in F. occidentalis and Thrips tobaci, the PCR diagnosis was developed for F. occidentalis. By means of Long and Accurate Polymerase Chain Reaction (LA-PCR), a complete mitochondrial genome sequence of F. occidentalis was determined, and analyzed by Editseq 7.1 and so on. All results showed as following:1. F.occidentalis was firstly found and reported in Nanjing. The results from morphological observation by means of optical and scanning electron microscope, and from PCR diagnostic test, proved that the alien invasive insect western flower thrips was occurred in 25 out of 54 plant varieties in Nanjing, Jiangsu Province, and indicated that the population density of western flower thrips were over 20% to the total thrips in 11 varieties, in 5 varieties the proprotion even higher than 30%. Survey shows the widespread occurrence of western flower thrips has occurred not only on landscape plants but also on vegetable crops, such as tomato and pepper.2. Scanning electron microscopy showed the great advantage on observation micro-structure over optical microscope, for example:segments of the antenna, head and pronotum, abdominal tergiteⅧand the fine three-dimensional information on the surface of insects, especiallly, the last one was obtained difficultly through optical microscope.3. In this study, flowers were cutted as the samples for flower-visiting thrips. And then species of thrips and the host plant were identified, quantities of thrips in the flowers could be counted completely in the lab, in this way the limitation of the method by knocking insects on disc could be eliminated in two aspects:thrips sampled partly and species of the host plant mis-identified.4. Rapid detection of PCR method showed that the method is sensitive, by which not only a single particle eggs can be detected, even 1/120 of the adults, and specificity, for the primers designed based on the reported COI sequence of Thrips tobaci and F. occidentalis, not only Thrips tobaci and F. occidentalis can be accurately detected respectively, but also the other thrips speceies close to them in evolution relationship were separated.5. The structure of complete mitochondrial genome of F.occidentalis is a circular, composed by 14 889 molecules of nucleotides. Its overall composition is 6 101 A (40.98%),1 646 C(11.06%),5 452 T(36.62%),1 690 G(11.35%), and the gene content includes 13 protein-coding genes,22 tRNA genes,2 rRNA genes and 3 control region.3 protein-coding genes and 3 tRNA genes are transcribed from L strand, and the other genes are transcribed from H strand. All protein-coding genes of the F.occidentalis mitochondrial genome start with a typical ATN codon. The usual TAA or TAG termination codons were found for 9 protein-coding genes, however, the ND1, ATP8, ND4 and ND4L genes have an incomplete terminati on codon (T) and the secondary structures of 22 tRNA genes were predicted by tRNAscan-SE.

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