title: Efficacy of genetically modified Bt toxins against insects with different genetic mechanisms of resistance.
abstract: Transgenic crops that produce Bacillus thuringiensis (Bt) toxins are grown widely for pest control, but insect adaptation can reduce their efficacy. The genetically modified Bt toxins Cry1AbMod and Cry1AcMod were designed to counter insect resistance to native Bt toxins Cry1Ab and Cry1Ac. Previous results suggested that the modified toxins would be effective only if resistance was linked with mutations in genes encoding toxin-binding cadherin proteins. Here we report evidence from five major crop pests refuting this hypothesis. Relative to native toxins, the potency of modified toxins was >350-fold higher against resistant strains of Plutella xylostella and Ostrinia nubilalis in which resistance was not linked with cadherin mutations. Conversely, the modified toxins provided little or no advantage against some resistant strains of three other pests with altered cadherin. Independent of the presence of cadherin mutations, the relative potency of the modified toxins was generally higher against the most resistant strains.
authors: Department of Entomology, University of Arizona, Tucson, Arizona, USA. brucet@cals.arizona.edu
authors: Bruce E
authors: BE
authors: Tabashnik
authors: Fangneng
authors: F
authors: Huang
authors: Mukti N
authors: MN
authors: Ghimire
authors: B Rogers
authors: BR
authors: Leonard
authors: Blair D
authors: BD
authors: Siegfried
authors: Murugesan
authors: M
authors: Rangasamy
authors: Yajun
authors: Y
authors: Yang
authors: Yidong
authors: Y
authors: Wu
authors: Linda J
authors: LJ
authors: Gahan
authors: David G
authors: DG
authors: Heckel
authors: Alejandra
authors: A
authors: Bravo
authors: Mario
authors: M
authors: Soberón
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis / Q000235:genetics* / Q000378:metabolism; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D015820:Cadherins / Q000235:genetics / Q000378:metabolism*; D004731:Endotoxins / Q000235:genetics* / Q000378:metabolism; D006460:Hemolysin Proteins / Q000235:genetics* / Q000378:metabolism; D007313:Insecta / Q000472:pathogenicity; D007305:Insecticide Resistance / Q000235:genetics; D009036:Moths / Q000469:parasitology; D009154:Mutation; D010572:Pest Control, Biological; D030821:Plants, Genetically Modified
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D015820:Cadherins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis