Title page for ETD etd-03022005-225622

Type of Document Dissertation
Author Whaley, Cory Miller
Author's Email Address cwhaley@vt.edu
URN etd-03022005-225622
Title Characterization of Acetolactate Synthase-Inhibiting Herbicide-Resistant Smooth Pigweed and Corn Weed Management Programs Utilizing Mesotrione in Combinations with Other Herbicides
Degree PhD
Department Plant Pathology, Physiology, and Weed Science
Advisory Committee
Advisor Name Title
Wilson, Henry P. Committee Chair
Brann, Daniel E. Committee Member
Hagood, Edward Scott Jr. Committee Member
Nessler, Craig L. Committee Member
Westwood, James H. Committee Member
  • thifensulfuron
  • ALS mutation
  • Amaranthus hybridus L.
  • weed control
  • nicosulfuron
  • triazolopyrimidine
  • imidazolinone
  • herbicide resistance
  • rimsulfuron
  • pyrimidinyloxybenzoate
  • atrazine
  • sulfonylurea
  • S-metolachlor
Date of Defense 2005-03-01
Availability unrestricted
Repeated use of acetolactate synthase (ALS)-inhibiting herbicides in recent years has resulted in the selection of 89 weed species resistant to these herbicides. One management strategy that can eliminate or slow the development of resistance is applying mixtures of herbicides with different modes of action. This research involved the characterization of ALS-inhibiting herbicide-resistant smooth pigweed (Amaranthus hybridus L.), as well as investigations on weed management programs in corn (Zea mays L.) utilizing mesotrione, a triketone, in mixtures with other herbicides. ALS-inhibiting herbicide-resistant smooth pigweed biotypes were collected from fields in Virginia, Delaware, Maryland, and Pennsylvania to evaluate response to ALS-inhibiting herbicides and to determine the molecular mechanisms of resistance. Sequencing of the ALS genes from these biotypes revealed two amino acid substitutions known to confer resistance, Ala122 to Thr and Ser653 to Asn, and one that has not been previously reported in plants, Asp376 to Glu. The smooth pigweed biotype with an Asp376 substitution displayed resistance to four classes of ALS-inhibiting herbicides that included imidazolinone (IMI), sulfonylurea (SU), pyrimidinylthiobenzoate (PTB), and triazolopyrimidine sulfonanilide (TP) chemistries. Transformation of this smooth pigweed ALS gene into Arabidopsis thaliana confirmed that the Asp376 substitution is responsible for the resistance. Other biotypes that had a substitution at Ala122 exhibited resistance to an IMI herbicide, little to no resistance to SU herbicides, and increased sensitivity to a PTB and a TP herbicide, whereas, biotypes that had a substitution at Ser653 exhibited high-level resistance to an IMI herbicide and lower resistance to PTB and SU herbicides. Experiments were also conducted to investigate the effectiveness of mesotrione in preemergence (PRE) and postemergence (POST) corn weed management programs in Virginia. Mesotrione applied PRE in mixtures with S-metolachlor and atrazine controlled common lambsquarters (Chenopodium album L.), smooth pigweed, common ragweed (Ambrosia artemisiifolia L.), and morningglory (Ipomoea spp.) species when a timely rainfall followed application. POST applications of mesotrione controlled common lambsquarters and smooth pigweed, but common ragweed and morningglory species were not always controlled. Common ragweed and morningglory species were controlled by mesotrione in a mixture with atrazine POST. Large crabgrass [Digitaria sanguinalis (L.) Scop.] and giant foxtail (Setaria faberi Herrm.) control was generally better when the ALS-inhibiting herbicides nicosulfuron plus rimsulfuron or rimsulfuron plus thifensulfuron plus atrazine were applied in a mixture with mesotrione. Mixtures of mesotrione with other POST herbicides in a total POST program produced corn yields comparable to standard PRE followed by POST weed management programs.
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  01cwhaley_TitleAbstract.pdf 86.05 Kb 00:00:23 00:00:12 00:00:10 00:00:05 < 00:00:01
  02cwhaley_Acknowledgments.pdf 54.74 Kb 00:00:15 00:00:07 00:00:06 00:00:03 < 00:00:01
  03cwhaley_TableofContents.pdf 120.21 Kb 00:00:33 00:00:17 00:00:15 00:00:07 < 00:00:01
  04cwhaley_Chapter1.pdf 133.80 Kb 00:00:37 00:00:19 00:00:16 00:00:08 < 00:00:01
  05cwhaley_Chapter2.pdf 268.12 Kb 00:01:14 00:00:38 00:00:33 00:00:16 00:00:01
  06cwhaley_Chapter3.pdf 146.12 Kb 00:00:40 00:00:20 00:00:18 00:00:09 < 00:00:01
  07cwhaley_Chapter4.pdf 137.56 Kb 00:00:38 00:00:19 00:00:17 00:00:08 < 00:00:01
  08cwhaley_Chapter5.pdf 168.52 Kb 00:00:46 00:00:24 00:00:21 00:00:10 < 00:00:01
  09cwhaley_Chapter6.pdf 151.72 Kb 00:00:42 00:00:21 00:00:18 00:00:09 < 00:00:01
  10cwhaley_Chapter7.pdf 155.73 Kb 00:00:43 00:00:22 00:00:19 00:00:09 < 00:00:01
  11cwhaley_Chapter8.pdf 79.43 Kb 00:00:22 00:00:11 00:00:09 00:00:04 < 00:00:01
  12cwhaley_vita.pdf 56.95 Kb 00:00:15 00:00:08 00:00:07 00:00:03 < 00:00:01

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