title: Inheritance of resistance to Bt canola in a field-derived population of Plutella xylostella.
abstract: Crops expressing Bacillus thuringiensis (Bt) insecticidal Cry proteins are grown on millions of hectares. Recommendations to delay resistance are based on a high expression/refugia strategy that aims to kill resistant heterozygotes and enable some susceptible insects to survive. Leaf-dip bioassays on F1 crosses of Malaysian populations of diamondback moth (Plutella xylostella (L)) showed that CrylAc resistance was not fully recessive. The survival of ca 50% of heterozygotes on Bt canola (Brassica napus L) leaves expressing low concentrations of CrylAc agreed with a non-fully-recessive model for resistance. Extrapolations based on log dose-logit mortality regressions for heterozygotes using leaf-dip bioassays showed that a relatively high level of expression, of ca 2000 ng CrylAc mg(-1) total leaf protein, would be required to give 90% mortality to heterozygotes. If high enough levels of expression of Bt toxin to kill heterozygotes cannot be achieved and maintained under field conditions, the effectiveness of the high-dose/refugia strategy would be reduced.
authors: Department of Biological Sciences, Imperial College London, Silwood Park campus, Ascot, Berkshire SL5 7PY, UK.
authors: Ali H
authors: AH
authors: Sayyed
authors: Tanja H
authors: TH
authors: Schuler
authors: Denis J
authors: DJ
authors: Wright
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics*; D001427:Bacterial Toxins / Q000096:biosynthesis / Q000235:genetics; D001681:Biological Assay; D029688:Brassica napus / Q000737:chemistry / Q000235:genetics / Q000469:parasitology*; D004731:Endotoxins / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics*; D005260:Female; D018506:Gene Expression Regulation, Plant; D017344:Genes, Insect; D005808:Genes, Recessive / Q000235:genetics; D006460:Hemolysin Proteins; D006579:Heterozygote; D007305:Insecticide Resistance / Q000235:genetics; D007814:Larva / Q000235:genetics / Q000254:growth & development; D008297:Male; D009036:Moths / Q000235:genetics* / Q000254:growth & development; D020412:Multifactorial Inheritance; D010572:Pest Control, Biological; D018515:Plant Leaves / Q000737:chemistry; D030821:Plants, Genetically Modified / Q000235:genetics / Q000469:parasitology*
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis