title: Esterase isoenzymes and insecticide resistance in Frankliniella occidentalis populations from the south-east region of Spain.
abstract: BACKGROUND
  Frankliniella occidentalis (Pergande) is among the most important crop pests in the south-east region of Spain; its increasing resistance to insecticides constitutes a serious problem, and understanding the mechanisms involved is therefore of great interest. To this end, F. occidentalis populations, collected from the field at different locations in south-east Spain, were studied in terms of total esterase activity and esterase isoenzyme pattern.
  
  
  RESULTS
  Individual thrips extracts were analysed by native polyacrylamide gel electrophoresis (PAGE) and stained for esterase activity with the model substrate alpha-naphthyl acetate. Significant correlations were found between resistance to the insecticides acrinathrin and methiocarb and the presence of a group of three intensely stained bands, named Triplet A. For each individual thrips extract, total esterase activity towards the substrates alpha-naphthyl acetate and alpha-naphthyl butyrate was also measured in a microplate reader. Insects possessing Triplet A showed a significantly higher alpha-naphthyl acetate specific activity and alpha-naphthyl acetate/alpha-naphthyl butyrate activity ratio. This observation allowed a reliable classification of susceptible or resistant insects either by PAGE analysis or by total esterase activity determination.
  
  
  CONCLUSIONS
  The PAGE and microplate assays described can be used as a monitoring technique for detecting acrinathrin- and methiocarb-resistant individuals among F. occidentalis field populations.
authors.affiliation: Departament de Biologia Funcional i Antropologia Física, Universitat de València, Valencia, Spain. neus.lopez@uv.es
authors.forename: Neus
authors.initials: N
authors.lastname: López-Soler
authors.forename: Amelia
authors.initials: A
authors.lastname: Cervera
authors.forename: Graham D
authors.initials: GD
authors.lastname: Moores
authors.forename: Rafael
authors.initials: R
authors.lastname: Martínez-Pardo
authors.forename: M Dolores
authors.initials: MD
authors.lastname: Garcerá
mesh_terms: D000818:Animals; D004591:Electrophoresis, Polyacrylamide Gel; D004950:Esterases / Q000378:metabolism*; D007313:Insecta / Q000201:enzymology*; D007305:Insecticide Resistance; D007306:Insecticides; D007527:Isoenzymes / Q000378:metabolism; D008714:Methiocarb; D009284:Naphthols / Q000378:metabolism; D011722:Pyrethrins; D013030:Spain; D005466:Fluorocarbons
chemical_list: D004950:Esterases; D007306:Insecticides; D007527:Isoenzymes; D008714:Methiocarb; D009284:Naphthols; D011722:Pyrethrins; C027876:alpha-naphthyl acetate; C029204:alpha-naphthyl butyrate; C119568:acrinathrin; D005466:Fluorocarbons