title: Variation in the sensitivity of Callosobruchus (Coleoptera: Bruchidae) acetylcholinesterase to the organophosphate insecticide malaoxon: effect of species, geographical strain and food type.
abstract: BACKGROUND
  Bruchid beetles, Callosobruchus species, are serious pests of economically important grain legumes; their activity in stores is often controlled by the use of synthetic insecticides. Esterases are known to be involved in insecticide resistance in insects. However, there is a dearth of information on esterase activity in the genus Callosobruchus. In this study, the effect of species, geographical strain and food type on the variation in acetylcholinesterase (AChE) activity and its inhibition by malaoxon (malathion metabolite) was investigated using an in vitro spectrophotometric method.
  
  
  RESULTS
  AChE activity varied significantly among species and strains and also among legume type used for rearing them. Generally, irrespective of species, strain or food type, the higher the AChE activity of a population, the higher is its inhibition by malaoxon. C. chinensis had the highest AChE activity of the species studied, and in the presence of malaoxon it had the lowest remaining AChE activity, while C. rhodesianus retained the highest activity.
  
  
  CONCLUSIONS
  A first-hand knowledge of AChE activity in regional Callosobruchus in line with the prevailing food types should be of utmost importance to grain legume breeders, researchers on plant materials for bruchid control and pesticide manufacturer/applicators for a robust integrated management of these bruchids.
authors.affiliation: Environmental Biology Section, School of Biological Sciences, University of Reading, Reading, Berks, UK.
authors.forename: Olajire A
authors.initials: OA
authors.lastname: Gbaye
authors.forename: Graham J
authors.initials: GJ
authors.lastname: Holloway
authors.forename: Amanda
authors.initials: A
authors.lastname: Callaghan
mesh_terms: D000110:Acetylcholinesterase / Q000378:metabolism; D000818:Animals; D001938:Brazil; D002163:Cameroon; D002800:Cholinesterase Inhibitors / Q000633:toxicity*; D001517:Coleoptera / Q000145:classification / Q000187:drug effects* / Q000201:enzymology* / Q000502:physiology; D007887:Fabaceae / Q000469:parasitology; D005247:Feeding Behavior / Q000187:drug effects; D019476:Insect Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D007306:Insecticides / Q000633:toxicity*; D008294:Malathion / Q000031:analogs & derivatives* / Q000633:toxicity; D010755:Organophosphates / Q000633:toxicity*; D010935:Plant Diseases / Q000469:parasitology; D013045:Species Specificity; D015006:Yemen
chemical_list: D002800:Cholinesterase Inhibitors; D019476:Insect Proteins; D007306:Insecticides; D010755:Organophosphates; C100082:malaoxon; D000110:Acetylcholinesterase; D008294:Malathion