title: Using an F(2) screen to monitor frequency of resistance alleles to Bt cotton in field populations of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae).
abstract: BACKGROUND
  In an effort to control the most devastating cotton pest, Helicoverpa armigera (Hübner), in Qiuxian County (Hebei, China), Bt cotton has been planted almost exclusively since 1998 in this area. Owing to the high insecticidal selection pressures in this region, monitoring of Bt resistance in H. armigera is necessary so that proactive actions can be implemented before field control measures fail. From 2003 to 2005, an F(2) screen was conducted in order to monitor Bt resistance in H. armigera populations collected from this area.
  
  
  RESULTS
  The F(2) screen showed that 15 out of 278 isofemale lines carried resistance alleles to Bt cotton. The resistance allele frequency in field populations of H. armigera ranged from 0.0119 to 0.0297, with an overall frequency of 0.0146 and a 95% confidence interval of 0.0084-0.0225 for the 3 year period. This value is greater than the value reported from 1999 (P < 0.05).
  
  
  CONCLUSIONS
  A fluctuating but overall increase in resistance allele frequency was detected in the field populations of H. armigera in Qiuxian County from 1999 to 2005. To prevent further increases in Bt resistance frequency in this pest, it is necessary to introduce Bt cotton expressing multiple Bt toxins and integrate this technology with other tactics for management of this key pest.
authors.affiliation: Department of Pesticide Science, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China.
authors.forename: Zhiping
authors.initials: Z
authors.lastname: Xu
authors.forename: Fengyi
authors.initials: F
authors.lastname: Liu
authors.forename: Jin
authors.initials: J
authors.lastname: Chen
authors.forename: Fangneng
authors.initials: F
authors.lastname: Huang
authors.forename: David A
authors.initials: DA
authors.lastname: Andow
authors.forename: Yanhua
authors.initials: Y
authors.lastname: Wang
authors.forename: Yu Cheng
authors.initials: YC
authors.lastname: Zhu
authors.forename: Jinliang
authors.initials: J
authors.lastname: Shen
mesh_terms: D000483:Alleles; D000818:Animals; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000494:pharmacology*; D004731:Endotoxins / Q000494:pharmacology*; D005260:Female; D003368:Gossypium / Q000235:genetics*; D006460:Hemolysin Proteins / Q000494:pharmacology*; D007305:Insecticide Resistance / Q000235:genetics*; D007306:Insecticides / Q000494:pharmacology; D008297:Male; D009036:Moths / Q000187:drug effects* / Q000235:genetics*; D013997:Time Factors
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; D007306:Insecticides; C030956:insecticidal crystal protein, Bacillus Thuringiensis