title: Cross-resistance study and biochemical mechanisms of thiamethoxam resistance in B-biotype Bemisia tabaci (Hemiptera: Aleyrodidae).
abstract: BACKGROUND
  B-biotype Bemisia tabaci (Gennadius) has invaded China over the past two decades. To understand the risks and to determine possible mechanisms of resistance to thiamethoxam in B. tabaci, a resistant strain was selected in the laboratory. Cross-resistance and the biochemical mechanisms of thiamethoxam resistance were investigated in the present study.
  
  
  RESULTS
  A 66.3-fold thiamethoxam-resistant B. tabaci strain (TH-R) was established after selection for 36 generations. Compared with the susceptible strain (TH-S), the selected TH-R strain showed obvious cross-resistance to imidacloprid (47.3-fold), acetamiprid (35.8-fold), nitenpyram (9.99-fold), abamectin (5.33-fold) and carbosulfan (4.43-fold). No cross-resistance to fipronil, chlorpyrifos or deltamethrin was seen. Piperonyl butoxide (PBO) and triphenyl phosphate (TPP) exhibited significant synergism on thiamethoxam effects in the TH-R strain (3.14- and 2.37-fold respectively). However, diethyl maleate (DEM) did not act synergistically with thiamethoxam. Biochemical assays showed that cytochrome P450 monooxygenase activities increased 1.21- and 1.68-fold respectively, and carboxylesterase activity increased 2.96-fold in the TH-R strain. However, no difference was observed for glutathione S-transferase between the two strains.
  
  
  CONCLUSIONS
  B-biotype B. tabaci develops resistance to thiamethoxam. Cytochrome P450 monooxygenase and carboxylesterase appear to be responsible for the resistance. Reasonable resistance management that avoids the use of cross-resistance insecticides may delay the development of resistance to thiamethoxam in this species.
authors: Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, PR China.
authors: Yuntao
authors: Y
authors: Feng
authors: Qingjun
authors: Q
authors: Wu
authors: Shaoli
authors: S
authors: Wang
authors: Xiaoli
authors: X
authors: Chang
authors: Wen
authors: W
authors: Xie
authors: Baoyun
authors: B
authors: Xu
authors: Youjun
authors: Y
authors: Zhang
mesh_terms: D000818:Animals; D004357:Drug Synergism; D005260:Female; D006430:Hemiptera / Q000145:classification* / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D007305:Insecticide Resistance; D007306:Insecticides / Q000494:pharmacology*; D008297:Male; D000073943:Neonicotinoids; D009574:Nitro Compounds / Q000494:pharmacology*; D010078:Oxazines / Q000494:pharmacology*; D000077922:Thiamethoxam; D013844:Thiazoles / Q000494:pharmacology*
chemical_list: D007306:Insecticides; D000073943:Neonicotinoids; D009574:Nitro Compounds; D010078:Oxazines; D013844:Thiazoles; D000077922:Thiamethoxam