| The codling moth Cydia pomonella L., Tortricidae, Lepidoptera, an important quarantine pest with global distribution, is mainly distributed in western Gansu and most parts of Xinjiang. This pest has spread eastward with harm of getting greater in recent years, which caused a serious threat to fruit production of Shaanxi and Eastern China. For purpose of codling moth, control and biology is main research work in China. Its molecular biology needs further research. In the current study, 59 COI segments of codling moth from 59 individual samples of 10 geographical populations were sequenced by using the universal primer COI of Lepidoptera, samples were collected from Urumqi, Hami, Kuitun, Jinghe, Yili, Kashi, Kuerle of Xinjiang and Jiuquan, Zhangye, Dunhuang of Gansu Province. Nucleotides composition, ratio of transition and transversion, genetic distance, considerable variable sites, nucleotide diversity and haplotype diversity of those segments were analyzed. Grapholitha molesta(Busck) was used as outgroup, molecular phylogenetic trees of different haplotypes were constructed with neighbour-Joining, maximum parsimony and maximum likelihood methods. Summarizing the outcomes,we can conclude the results as follows:1. The results of sequence variation analyses showed that the aligned fragments of COⅠfrom the codling moth was 450bp in length, including 433 conservative 17 variable sites, variable sites accounted for 3.78% of total base. Mean A%, T%, G% and C% content for the sequences were 28.5%, 39.5%, 14.0% and 18.1%, the percentage of A%+T%(68%) was significantly higher than G%+C%(32.1%). Transition of sequences was higher than transversion.2. In total, 10 haplotypes were identified within 59 COI segments of Cydia pomonella L., and 3 of them exclusive. The topological structure of 10 haplotypes in molecular phylogenetic trees indicates these geographical populations of codling moth are clearly divided in 3 clades. Both the exclusive haplotype and phylogenetic trees of haplotypes showed that genetic differences of COI gene existed among different populations. The genetic distance among 10 geographical populations of codling moth were 0 ~0.014. It shows that all of the genetic variations of codling moth populations were not at species level, only at infraspecies level.3. Among 10 populations of codling moth in this study, nucleotide diversity and haplotype diversity of Yili population was significantly higher than other populations. Therefore, in terms of the resident orders of these 10 geographical populations, Cydia pomonella L. had been resident in Yili earlier than in other 9 areas.4. The Dunhuang population of Cydia pomonella L. represented high nucleotide diversity only lower than Yili population. Through the analysis of haplotypes distribution frequencies in different populations and phylogenetic trees of haplotypes, we can find that Yili was one of the source for Dunhuang population of Cydia pomonella L..5. The Jiuquan population of Cydia pomonella L. represented higher nucleotide diversity. The analysis of haplotypes distribution frequencies in Jiuquan and Dunhuang populations and phylogenetic trees of haplotypes, suggested that Jiuquan population had lower possibility on spreading from Dunhuang population. Through the analysis of haplotypes distribution frequencies in different populations, we can find that Hami was one of the source area for Jiuquan population of Cydia pomonella L..Carposina niponensis, Grapholitha molesta(Busck) and Grapholitha funebrana are three common borer species in apple orchards of China. And young larve of these three borers are extraordinary similar on morphology with codling moth, Cydia pomonella L.. In the current study, COI segments of these 4 borers were sequenced by using the universal primer COI of Lepidoptera. A specific primer to codling moth was designed based on the COI sequence alignment. And its efficiency in diagnoses had been tested. The result shows that PCR with this primer is positive to codling moth only. |
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