Activity Of Permethrin To Mosquito Culex Quinquefasciatus And Cloning And Expression Identification Of Permethrin Associated Genes

Insect vectors could seriously harm human health.According to the statistical estimate, 1/2 infectious diseases are transmitted by insect vectors.Although many important advances continually were made in the development of alternative control pathway, pesticide always remains a severally predominant part in the broadly and continuously using.Thus it can not avoid causing development of resistance to insecticides.Mosquito is a very important medical insect involved in transmitting diseases and harming human health.Therefore,it is very impending to study the resistance mechanisms and proper resistance management.In this thesis,the susceptibility of permethrin were determined for different instar larvae and adults of mosquito permethrin-susceptible(S-Lab) and -resistant strains (BamCq,MamCq,MamCqâ…¡,HamCq and HamCqâ…¨).HamCq,HamCqâ…¨,MamCq, MamCqâ…¡and BamCq larvae showed resistance to permethrin with resistance ratio of 1, 26,4,15 and 10-fold in 1^st instar;3,185,7,9 and 45-fold in 2^nd instar;3,225,3,8 and 59-fold in 3^rd instar;10,748,2,9 and 77-fold in 4^th instar,respectively,compared with the susceptible S-Lab strain.The female adults of resistance strains showed resistance ratio of 3,64,0.3,0.7 and 1.3-fold;the male adults of resistence strians showed resistance ratio of 2,67,0.5,0.67 and 3-fold,respectively.The LD₅₀(μg/individual) of female are higher than male.The toxicity of SCPIs with and without permethrin to mosquito strains was determined. The results showed that LC₅₀ of SCPI-1 to S-Lab,HamCqâ…¨,MamCqâ…¡and BamCq are 1.710,2.601,1.323 and 2.738μM/mL,LC₅₀ of the SCPI-2 are 0.306,0.142,0.353 and 1.276μM/mL.SCPI-1 and SCPI-2 also enhanced toxicity of permethrin to S-lab 5.3-fold and 3.2-fold,and to MamCqâ…¡,HamCqâ…¨and BamCq 4,16.8,4-fold and 2,4.8,1.6-fold, respectivily.Two new cytochrome P450 genes fragments were isolated from HamCqâ…¨strain and identified as CYP9 family.Real-time PCR approach were used to detect the expression differences between larvae and adults of permethrin-susceptible(S-Lab) strain and -resistance strains(HamCq and HamCqâ…¨),respectivily.Comparison of P450-18 expression between HamCqâ…¨,HamCq and S-Lab strains indicated that there were higher expression(3 and 6-fold) in adults,and expression were much higher(110 and 4-fold) in larvae,respectively;P450-26 were no difference in their adults,but expression were much higher(194 and 48-fold) in larvae,respectively.Furthermore,the highest expression level of the two new genes were in the 4^th larvae of all strains.