High-level resistance to Bacillus thuringiensis toxin CrylAc and cadherin genotype in pink bollworm

Bruce E. Tabashnik, Robert W. Biggs, Jeffrey A. Fabrick, Aaron J. Gassmann, Timothy J. Dennehy, Yves Carrière, Shai Morin

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

Resistance to transgenic cotton, Gossypium hirsutum L., producing Bacillus thuringiensis (Bt) toxin CrylAc is linked with three recessive alleles of a cadherin gene in laboratory-selected strains of pink bollworm, Pectinophora gossypiella (Saunders), a major cotton pest. Here, we analyzed a strain (MOV97-R) with a high frequency of cadherin resistance alleles, a high frequency of resistance to 10 μg of CrylAc per milliliter of diet, and an intermediate frequency of resistance to 1,000 μg of CrylAc per ml of diet. We selected two strains for increased resistance by exposing larvae from MOV97-R to diet with 1,000 μg of CrylAc per ml of diet. In both selected strains, two to three rounds of selection increased survival at 1,000 μg of CrylAc per ml of diet to at least 76%, indicating genetic variation in survival at this high concentration and yielding >4,300-fold resistance relative to a susceptible strain. Variation in cadherin genotype did not explain variation in survival at 1,000 μg of CrylAc per ml of diet, implying that one or more other loci affected survival at this concentration. This conclusion was confirmed with results showing that when exposure to CrylAc stopped, survival at 1,000 μg of CrylAc per ml of diet dropped substantially, but survival at 10 μg CrylAc per ml of diet remained close to 100% and all survivors had two cadherin resistance alleles. Although survival at 1,000 μg of CrylAc per ml of diet is not required for resistance to Bt cotton, understanding how genes other than cadherin confer increased survival at this high concentration may reveal novel mechanisms of resistance.

Original languageEnglish (US)
Pages (from-to)2125-2131
Number of pages7
JournalJournal of economic entomology
Volume99
Issue number6
DOIs
StatePublished - Dec 2006

Keywords

  • Bacillus thuringiensis
  • Genetically modified crops
  • Genetics
  • Pectinophora gossypiella
  • Resistance

ASJC Scopus subject areas

  • Ecology
  • Insect Science

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