Understanding Transgene Flow from Bt Cotton into Non-Bt Cotton Fields and its Consequences for Pest Resistance Evolution

Persistent Link:
http://hdl.handle.net/10150/196057
Title:
Understanding Transgene Flow from Bt Cotton into Non-Bt Cotton Fields and its Consequences for Pest Resistance Evolution
Author:
Heuberger, Shannon
Issue Date:
2010
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Refuges of non-Bacillus thuringiensis (Bt) cotton are used to delay Bt resistance in several key insect pests. In 2004, I discovered that Bt cotton plants sometimes enter refuges via the seed bag, and hypothesized that this type of gene flow could have important effects on resistance evolution in insect pests. In the research described herein, I investigated the sources of Bt plants in the non-Bt cotton seed supply and assessed the potential implications of this gene flow on pest resistance evolution. I report results from an empirical study of gene flow in 15 non-Bt cotton seed production fields, as well as results from simulation modeling studies of gene flow from one-toxin and two-toxin Bt cotton. The current policy on gene flow from genetically engineered crops in the United States is also reviewed, including the implications of my research findings for policymakers. Key findings of this study included the prominent role of seed-mediated gene flow in the seed-production setting, and the utility of a geographic information system (GIS) ring analysis approach for describing pollen-mediated gene flow in cotton fields. Modeling results indicated that high rates of gene flow of Bt cotton into refuges could have large effects on pest resistance evolution under certain sets of assumptions, particularly in parts of the world where farm-saved seed is planted year after year in cotton fields. It appears that some of these effects could be mitigated by using non-cotton refuges or by using plants that contain linked transgenes that confer multiple toxins. There are no clear regulations in the United States regarding gene flow of Bt cotton into refuge seed or into seed production fields of non-Bt cotton, as Bt cotton has been deregulated following extensive safety testing. Nevertheless, results from this research suggest that limiting gene flow into refuge seed could be important for sustaining the efficacy of Bt cotton against targeted insect pests in regions where refuges are used.
Type:
text; Electronic Dissertation
Keywords:
Bt cotton; gene flow; refuge; resistance; simulation model; transgenic crops
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Entomology; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Carriere, Yves
Committee Chair:
Carriere, Yves

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleUnderstanding Transgene Flow from Bt Cotton into Non-Bt Cotton Fields and its Consequences for Pest Resistance Evolutionen_US
dc.creatorHeuberger, Shannonen_US
dc.contributor.authorHeuberger, Shannonen_US
dc.date.issued2010en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractRefuges of non-Bacillus thuringiensis (Bt) cotton are used to delay Bt resistance in several key insect pests. In 2004, I discovered that Bt cotton plants sometimes enter refuges via the seed bag, and hypothesized that this type of gene flow could have important effects on resistance evolution in insect pests. In the research described herein, I investigated the sources of Bt plants in the non-Bt cotton seed supply and assessed the potential implications of this gene flow on pest resistance evolution. I report results from an empirical study of gene flow in 15 non-Bt cotton seed production fields, as well as results from simulation modeling studies of gene flow from one-toxin and two-toxin Bt cotton. The current policy on gene flow from genetically engineered crops in the United States is also reviewed, including the implications of my research findings for policymakers. Key findings of this study included the prominent role of seed-mediated gene flow in the seed-production setting, and the utility of a geographic information system (GIS) ring analysis approach for describing pollen-mediated gene flow in cotton fields. Modeling results indicated that high rates of gene flow of Bt cotton into refuges could have large effects on pest resistance evolution under certain sets of assumptions, particularly in parts of the world where farm-saved seed is planted year after year in cotton fields. It appears that some of these effects could be mitigated by using non-cotton refuges or by using plants that contain linked transgenes that confer multiple toxins. There are no clear regulations in the United States regarding gene flow of Bt cotton into refuge seed or into seed production fields of non-Bt cotton, as Bt cotton has been deregulated following extensive safety testing. Nevertheless, results from this research suggest that limiting gene flow into refuge seed could be important for sustaining the efficacy of Bt cotton against targeted insect pests in regions where refuges are used.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectBt cottonen_US
dc.subjectgene flowen_US
dc.subjectrefugeen_US
dc.subjectresistanceen_US
dc.subjectsimulation modelen_US
dc.subjecttransgenic cropsen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineEntomologyen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorCarriere, Yvesen_US
dc.contributor.chairCarriere, Yvesen_US
dc.contributor.committeememberTabashnik, Bruce E.en_US
dc.contributor.committeememberDeGrandi-Hoffman, Gloriaen_US
dc.contributor.committeememberPalumbo, Johnen_US
dc.identifier.proquest11352en_US
dc.identifier.oclc752261213en_US
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