Thesis (Ph. D.)--Dept. of Agronomy and Farming Systems, The University of Adelaide, Roseworthy Campus, 1998. / Includes bibliographical references (leaves 128-146).

Thesis (M.S.)--University of Missouri-Columbia, 2008. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on July 8, 2009) Includes bibliographical references.

Thesis (Ph. D.)--Jyväskylä Yliopisto, 1980. / Includes bibliographical references (p. 46-57).

Thesis (M.Sc.) - Carleton University, 2007. / Includes bibliographical references (p. 130-139). Also available in electronic format on the Internet.

Thesis (Ph. D.)--Jyväskylä Yliopisto, 1980. / Bibliography: p. 46-57.

Thesis (M.S.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on October 26, 2007) Vita. Includes bibliographical references.

Bibliography: leaves 151-172.

Triasulfuron (3-(6-methoxy-4-methyl-1,3,5-triazin-2-yl)-1-[2-(2- chloroethoxy)-phenylsulfonyl)-urea} is a new pre- and post-emergence herbicide developed for the control of broad-leaved_'Teeds and some grasses in small grain cereals at rates of 10-20gha . Oilseed rape, pea, broad bean, Senecio vulgaris, Veronica persica, Lolium renne, Poa annua, Poa trivialis and prates were severely a ed 5y pre-emergence and post-emergence applications of triasulfuron but wheat and barley were much more resistant. The development of injury symptoms was generally slow and was characterized by an initial growth retardation followed by chlorosis and necrosis with death occuring 3-4 weeks after application. The herbicide had a flat dose-response curve throughout the investigations. Wheat and barley showed greater tolerance to post-emergence than to pre-emergence applications. Pre-emergence applications of triasulfuron reduced tiller numbers in barley and wheat but application of the herbicide at the 2-3 leaf stage stimulated the outgrowth of tiller buds but this effect was temporary and was not the result of visible physical damage to the shoot meristem. There was no intra-specific variability between cultivars of wheat and barley. Grain yield and other yield components of spring barley were not affected by post-emergence treatments of triasulfuron. Triasulfuron had high activity through the soil and both the roots and subterranean shoots of developing seedlings absorbed the herbicide from the soil. The bioactivity and mobility of the herbicide down the soil profile was inversely related to the organic matter content of the soil. The amount and frequency of rainfall directly influenced the rate of leaching of the herbicide down the soil profile. Comparisons of the rates of disappearance of triasulfuron in autoclaved and non-autoclaved soils suggested the involvement of a biglogical degragation pathway. Triasulfuron disappeared faster at 30 °C than at 10 °C and higher moisture levels enhanced the rate of breakdown. Studies on the mode of action of triasulfuron indicated that the herbicide acts by inhibiting cell division in susceptible plants. Evidence suggested that the inhibition occurred during interphase rather than during the mitotic sequence. The addition of a 1: 1 mixture of isoleucine and valine to the treatment solution prevented the inhibition of cell division at the root tips of broad bean.

New transgenic crops are currently being developed which will be tolerant to dicamba and 2,4-D herbicides. This technology could greatly benefit producers who are impacted by weed species that have developed resistance to other herbicides, like glyphosate-resistant Palmer Amaranth. Adoption of this new technology is likely to be rapid and widespread which will lead to an increase in the amount of dicamba and 2,4-D applied each season. It is well-documented that these herbicides are very injurious to soybeans, cotton, tomatoes, and most other broadleaf crops, and their increased use brings along increased chances of physical spray drift onto susceptible crops. Because of these risks, research is being conducted on new herbicide formulation/spray nozzle combinations to determine management options which may minimize physical spray drift.

Herbicide resistance is increasing in incidence among weed populations and poses a threat to food security. In Sunflower County, MS, a population of junglerice was identified with resistance to four herbicides, fenoxaprop-P-ethyl, imazamox, quinclorac, and propanil, each representing a different mechanism of action. The target site of fenoxaprop-P-ethyl, acetyl coenzyme A carboxylase (ACCase), was investigated. The ACCase contained none of the known resistance-conferring point mutations and an enzyme assay revealed no difference in response to increasing levels of fenoxaprop-P-ethyl between the resistant biotype and a sensitive biotype, indicating that the ACCase enzyme in the resistant biotype was sensitive to the herbicide. Whole-plant dose response assays in the presence and absence of cytochrome P450 and glutathione-S-transferase (GST) inhibitors did not increase efficacy of fenoxaprop-P-ethyl in the resistant biotype. However, when malathion, a cytochrome P450 inhibitor, was applied with imazamox or quinclorac, a reduction in resistance was observed in the resistant biotype, suggesting that a cytochrome P450 was important to the resistance mechanism for these two herbicides. RNA was isolated from the resistant and sensitive biotypes before and one hour after imazamox treatment for RNA-seq analysis. The reads from all samples were pooled to assemble the first E. colona leaf transcriptome. Differential gene expression analysis comparing untreated and treated samples for both biotypes revealed that several stress response genes were upregulated following herbicide exposure. A time course examining six of these genes showed that expression peaked between 4 and 12 hours and then dropped to untreated levels by 48 hours. Comparison of untreated resistant and sensitive plants revealed that a kinase and GST were significantly upregulated in the resistant biotype and an F-box protein was significantly downregulated. SNP analysis of cytochrome P450 sequences identified several nonsynonymous point mutations of interest including two transcripts that had premature stop codons in the sensitive but not the resistant biotype. These transcripts and their products should be the subject of future studies to determine if and how they are involved in resistance.