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Quizalofop-resistant wheat: biochemical characterization of the AXigen™ trait and corresponding metabolism

dc.contributor.authorBough, Raven A., author
dc.contributor.authorDayan, Franck E., advisor
dc.contributor.authorGaines, Todd A., committee member
dc.contributor.authorHaley, Scott, committee member
dc.contributor.authorPearce, Stephen, committee member
dc.description.abstractA new weed management tool in wheat, the CoAXium™ Wheat Production System, incorporates quizalofop-resistant wheat, a specialized formulation of quizalofop (Aggressor™), and a stewardship management program for effective management of annual grasses with otherwise limited control options. The AXigen™ trait confers resistance primarily through a single-point mutation in ACC1. The mutation causes an alanine to valine substitution at position 2004 in wheat acetyl-CoA carboxylase (ACCase) relative to the Alopecurus myosuriodes reference. Through greenhouse and biochemical studies paired with protein homology modelling and simulations, the research presented herein provides strong evidence that a conformational change imparted by the amino acid substitution results in quizalofop-resistant ACCase. Conversely, the mutation conveys negative cross-resistance to haloxyfop, a similar herbicide to quizalofop with a smaller molecular volume. The remaining research objectives focus on quizalofop metabolism in CoAXium™ wheat. Liquid chromatography-mass spectrometry measurements of quizalofop content over time from liquid demonstrate cooler temperature conditions (4.5°C) delay quizalofop metabolism by 4 times compared to warmer temperature conditions (19°C). Reduced temperatures also delay quizalofop metabolism to the same extent in the following annual grass weed species: Aegilops cylindrica, Bromus tectorum, and Secale cereale. Further, additional studies suggest herbicide metabolism mechanisms enhance overall CoAXium™ wheat quizalofop resistance. Despite similar ACCase resistance, resistant winter and spring wheat varieties convey varying degrees of whole-plant resistance. In winter wheat but not spring wheat, increased resistance corresponds to a shorter quizalofop half-life, implying faster metabolism boosts overall resistance. Treatment of resistant spring wheat varieties with cloquintocet, a metabolism-boosting safener, increases overall resistance. Follow-up differential expression analysis of cloquintocet-treated plants may support differential metabolism findings and lead to identification of putative candidate genes associated with upregulated herbicide metabolism, such as cytochrome P450 monooxygenases, glutathione-S-transferases, and glycosyltransferases.
dc.format.mediumborn digital
dc.format.mediumdoctoral dissertations
dc.publisherColorado State University. Libraries
dc.rightsCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see
dc.subjectacetyl-CoA carboxylase
dc.titleQuizalofop-resistant wheat: biochemical characterization of the AXigen™ trait and corresponding metabolism
dcterms.rights.dplaThis Item is protected by copyright and/or related rights ( You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s). Biology State University of Philosophy (Ph.D.)


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