Outcrossed cottonseed and adventitious Bt plants in Arizona refuges

Shannon Heuberger, Christine Yafuso, Gloria Degrandi-Hoffman, Bruce E. Tabashnik, Yves Carrière, Timothy J. Dennehy

Research output: Contribution to journalArticlepeer-review

19 Scopus citations


Outcrossing of non-Bt cotton (Gossypium hirsutum (L.)) in refuges by transgenic cultivars could reduce the efficacy of refuges for delaying resistance in seed-feeding pests. Based on reports that outcrossing decreased as distance from Bt cotton increased in small-scale studies, we hypothesized that increasing refuge width or distance from Bt fields would reduce outcrossing. In a large-scale study in Arizona, we quantified Bt seed in refuges of experimental and commercial fields, comparing outcrossing between in-field (narrow) and external (wide) refuges and among rows of refuges at various distances from Bt fields. Some refuges, including those in tightly controlled experimental plots, contained up to 8% adventitious Bt plants. Some, but not all, Bt plants likely resulted Bt from seed in the non-Bt seed bags. We did not detect a difference in outcrossing between in-field and external refuges. However, statistical power was low because outcrossing was low ( 0.4% of seeds) in both treatments. Higher outcrossing levels ( 4.6% of seeds) were observed in the studies measuring outcrossing at various distances from Bt fields, yet outcrossing did not decrease as the distance from Bt fields increased. We hypothesize that Bt plants in refuges cross-pollinated surrounding non- plants, overshadowing the expected association between distance from Bt fields and outcrossing.

Original languageEnglish (US)
Pages (from-to)87-96
Number of pages10
JournalEnvironmental Biosafety Research
Issue number2
StatePublished - Apr 2008


  • Adventitious plants
  • Bt cotton
  • Gene flow
  • Outcrossing
  • Refuge

ASJC Scopus subject areas

  • Biotechnology
  • Biomedical Engineering
  • Safety, Risk, Reliability and Quality
  • Environmental Science(all)
  • Agricultural and Biological Sciences(all)
  • Safety Research


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