The Study On Molecular Ecology Characteristics Of Knockdown Resistance (kdr) To Pyrethroid Of Culex Pipiens Pallens

Culex pipiens pollens is a principal vector mosquito in northern China. Because of intensive usage of pyrethroid in pest control, the resistance of Cx. pipiens pallens to pyrethroid developed rapidly and widely in many area of China. It's necessary to reveal the mechanism for surveillance and management of mosquito resistance. Knockdown resistance (kdr) is characterized by the direct interaction between pyrethroid and the target site of insects, which will be well done for displaying the occurrence and development of pyrethroid resistance . It was studied the molecular ecological characteristics of the pyrethroid resistance of lab and natural populations of Cx. pipiens pallens in this research, the results were as followed: 1. The substitution of L1014F in IIS6 segment of sodium channel is the molecular basis of kdr resistance of Cx pipiens pallens through resistance selection and on mosquito populations , RT-PCR, and sequence analysis.2. Allele specific PCR (AS-PCR) protocol was developed for the estimation of kdr allele and another new approach polymerase chain reaction followed by labeled allele-specific oligonucleotide hybridization (ASO-PCR) was also developed for checking the accuracy of AS-PCR. The accordance percentage between two protocols was up to 97.2%. Sequencing alignment proved the two methods had both identity and sensitivity.3. A deltamethrin resistance strain and an esbiothrin resistance strain was selected respectively on a natural population by deltamethrin and esbiothrin, called DEL strain and EBT strain.4. It was found that the increasing style of resistance in DEL strain was linear but was logarithmic in EBT strain during selection. The increasing speed in DEL strain was faster than that in EBT strain.5. It was metabolic resistance that acted an important role in DEL strain but was kdr resistance in EBT strain, based on PBO synergic experiments and kdr allele frequency detection.6. The realized population heritability of resistance in DEL strain and EBT strain was 0.3804 and 0.4192 respectively. The conclusion of resistance balance state in DEL strain but conversely in EBT strain was based upon that phenotypic variance of DEL strain (0.42) was higher than EBT strain (0.19).7. It was showed that the correlation of the prevalence of kdr frequency was significant with the pyrethroid resistance level in natural populations, which suggested that the kdr frequency can be a molecular marker served for resistance monitor on mosquito population.8. It was revealed that there was higher migration frequency between compared populations (total Nm was 6.11 across all populations) based on the genetic differentiation among natural populations with the microsatellite loci isolated from the genome pool. It was implied that the gene flow among populations will affect the kdr gene expanding, which will bring on the change of the resistance development among population.