Association between resistance to Bt cotton and cadherin genotype in pink bollworm

Bruce E. Tabashnik*, Robert W. Biggs, Dawn M. Higginson, Scottie Henderson, Devika C. Unnithan, Gopalan C. Unnithan, Christa Ellers-Kirk, Mark S. Sisterson, Timothy J. Dennehy, Yves Carrière, Shai Morin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

83 Scopus citations


Two strains of pink bollworm, Pectinophora gossypiella (Saunders), each derived in 1997 from a different field population, were selected for resistance to Bacillus thuringiensis (Bt) toxin Cry1Ac in the laboratory. One strain (MOV97-R) originated from Mohave Valley in western Arizona; the other strain (SAF97-R) was from Safford in eastern Arizona. Relative to a susceptible laboratory strain, Cry1Ac resistance ratios were 1700 for MOV97-R and 520 for SAF97-R. For the two resistant strains, larval survival did not differ between non-Bt cotton and transgenic cotton producing Cry1Ac. In contrast, larval survival on Bt cotton was 0% for the two unselected parent strains from which the resistant strains were derived. Previously identified resistance (r) alleles of a cadherin gene (BtR) occurred in both resistant strains: r1 and r3 in MOV97-R, and r1 and r2 in SAF97-R. The frequency of individuals carrying two r alleles (rr) was 1.0 in the two resistant strains and 0.02 in each of the two unselected parent strains. Furthermore, in two hybrid strains with a mixture of susceptible (s) and r alleles at the BtR locus, all survivors on Bt cotton had two r alleles. The results show that resistance to Cry1Ac-producing Bt cotton is associated with recessive r alleles at the BtR locus in the strains of pink bollworm tested here. In conjunction with previous results from two other Bt-resistant strains of pink bollworm (APHIS-98R and AZP-R), results reported here identify the cadherin locus as the leading candidate for molecular monitoring of pink bollworm resistance to Bt cotton.

Original languageAmerican English
Pages (from-to)635-644
Number of pages10
JournalJournal of Economic Entomology
Issue number3
StatePublished - Jun 2005


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


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