Cadherin-based resistance to Bacillus thuringiensis cotton in hybrid strains of pink bollworm: Fitness costs and incomplete resistance

Yves Carrière, Christa Ellers-Kirk, Robert W. Biggs, Megan E. Nyboer, Gopalan C. Unnithan, Timothy J. Dennehy, Bruce E. Tabashnik

Research output: Contribution to journalArticle

39 Scopus citations

Abstract

Recessive resistance to Bacillus thuringiensis (Bt) cotton, Gossypium hirsutum L., in laboratory-selected strains of pink bollworm, Pectinophora gossypiella (Saunders), is associated with three resistance alleles (r1, r2, and r3) of a cadherin gene. Previous experiments based on measurement of fitness components in Bt-resistant and Bt-susceptible strains revealed that fitness costs and incomplete resistance are associated with resistance. Here, we used two hybrid strains of pink bollworm, each containing a mixture of susceptible and resistant individuals, and polymerase chain reaction (PCR) amplifications to test the association between cadherin genotype and fitness components for individuals sharing a common genetic background. All survivors on Bt cotton had two r alleles, confirming that recessive cadherin alleles are tightly linked with resistance to Bt cotton. On non-Bt cotton, significantly greater developmental time for rr than ss larvae indicated a recessive fitness cost, but costs did not affect survival or pupal weight. Incomplete resistance was manifested as longer developmental time, lower survival, and smaller pupal weight in rr individuals developing on Bt cotton compared with non-Bt cotton. As in previous experiments, no significant variation in performance on Bt cotton was detected among rr genotypes. However, a meta-analysis of data from seven experiments revealed that survival on Bt cotton relative to non-Bt cotton was lower in r2r3 and higher in r1r2 compared with the other rr genotypes. Assessment of fitness components associated with cadherin genotypes in hybrid strains of pink bollworm confirms that recessive resistance to Bt cotton is associated with recessive fitness costs and incomplete resistance.

Original languageEnglish (US)
Pages (from-to)1925-1935
Number of pages11
JournalJournal of economic entomology
Volume99
Issue number6
StatePublished - Dec 1 2006
Externally publishedYes

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Keywords

  • Bacillus thuringiensis
  • Fitness costs
  • Genetically modified crops
  • Pectinophora gossypiella
  • Resistance

ASJC Scopus subject areas

  • Ecology
  • Insect Science

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