Theses & Dissertations - Retrospective (historical)

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This collection contains a growing number of digitized theses and dissertations published by University of Guelph graduate students prior to 2011.

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Now showing 1 - 5 of 4735
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    Detection of Leptosphaeria Korrae, The Causal Agent of Necrotic Ring Spot, and its Occurrence in Southern Ontario
    (University of Guelph, Jan-94) O'Gorman, Daniel; Hsiang, Tom
    Isolations from 122 suspected necrotic ring spot (NRS) samples collected throughout southern Ontario, were used to confirm the presence of the disease in the province. Based on morphology of the sexual structures, Leptosphaeria korrae, the causal agent of NRS, was confirmed in 17 Ontario counties. To increase the efficiency of pathogen detection, an assay based on the polymerase chain reaction (PCR), was tested using the primer pair, LK17S/5.8SC, selected from the internal transcribed spacer region 1 of L. korrae ribosomal DNA. Specific amplification of L. korrae DNA was obtained, while no amplification occurred with DNA isolated from 15 other fungal species or healthy Kentucky bluegrass, the major host of NRS. The use of PCR with RAPD (random amplified polymorphic DNA) primers, allowed detection of genetic variability in L. korrae single spore siblings and isolates collected from a single field site. The distribution pattern of polymorphic isolates at the field site suggests both mycelial growth and released ascospores were involved in the spread of NRS.
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    Screening Ecotypes of Poa Annua var. Reptans for Susceptibility to Pink Snow Mould Caused by Microdochium nivale
    (University of Guelph, Apr-05) Cunningham, Martha; Dionne, Julie; Hsiang, Tom
    Annual bluegrass (Poa annua) ecotypes collected from golf course putting greens were evaluated for resistance to pink snow mould (Microdochium nivale) under natural and controlled conditions. Field plots consisted of thirty ecotypes transplanted into existing creeping bentgrass (Agrostis stolonifera) putting greens in the fall, which allowed the turf to cold acclimate. Inoculation occurred in early winter. Weekly visual evaluation conducted immediately after snowmelt over six weeks revealed significant differences in the ability of the ecotypes to resist pink snow mould attack and to recover after snowmelt. Cold chamber plots consisted of the same ecotypes used in the field study plus two bentgrasses transplanted into tubes. The ecotypes were acclimated in a cold chamber before they were inoculated with infested wheat bran. Visual evaluation during the incubation period revealed significant differences in the ability of the ecotypes and the bentgrasses to resist pink snow mould attack.
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    Bioassays to Detect Dissipation and Efficacy of Benomyl on Turf
    (University of Guelph, Nov-93) Liu, Leon Xuecai; Hsiang, Tom
    Paper disc, soil-agar pellet, turfgrass-agar pellet, thatch-agar pellet, and sample agar mixture bioassays were developed and evaluated for detection of the fungicide benomyl and its major fungitoxic product methyl 2-benzimidazole carbamate (MBC) in leachate, soil, turfgrass clippings, and thatch. The bioassays could detect benomyl and MBC residues with a limit of detection of 0.2 μg/g and a limit of quantitation of 0.5 μg/g. In vitro soil and thatch degradation studies showed a half-life for MBC of approximately 18 days in thatch and 4 to 5 weeks in soil, depending on soil type. An adsorption equilibrium with benomyl in solution was reached within 1 h for thatch and 2 to 4 h for soils. MBC adsorbed by thatch was as much as twice that adsorbed by a Fox sandy loam which may represent a typical soil found on golf courses in Southern Ontario. When MBC was applied at 10 μg/g, up to 90% of the chemical in thatch and 68% in soil were not extractable with water. Methanol could extract up to three times the fungicide from soil or thatch as could water. Laboratory and field experiments showed that the wetting agent Aqua-Gro (AG) (polyoxyethylene ester and ether of cyclic acid and alkylated phenols) significantly reduced adsorption of benomyl by creeping bentgrass thatch. With AG, significantly less fungicide was initially adsorbed and significantly more fungicide was later desorbed from the thatch layer by 20 mm of water irrigation. Aqua-Gro increased movement, uptake, and biological availability of the fungicide and resulted in a higher residue level of fungicide in the grass clippings. Tersan 1991 (50% benomyl) applied at 2 kg/ha with AG gave control of dollar spot disease as good as the full rate (3 kg/ha) without AG. Field studies also showed that core cultivation 1 or 7 days before fungicide application gave better and longer-lasting uptake of the fungicide by turfgrass and resulted in better control of dollar spot disease. Core cultivation one day before fungicide treatment gave the best results both in long-lasting uptake of benomyl and control of dollar spot disease.
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    National Postcolonial: Representations of the enemy within in Canada's national newspapers
    (University of Guelph, ) Smolash, Wendy Naava; Heble, Ajay
    This thesis examines current constructions of "the enemy within" in Canada's national newspapers through an analytical framework inspired by Noam Chomsky, Edward Said, and other theorists including Critical Whiteness scholars such as Richard Dyer. It theorizes national newspaper narratives through a counterdiscursive close reading of coverage of the "Project Thread" arrests over a three-month period in 'The Globe and Mail ' and 'The National Post'. This coverage of the "preventative detentions" of international students from Pakistan and India reveals patterns that resemble the racialized representation of bodies deemed "the enemy within" during World Wars One and Two. Through such factors as repetitions, juxtaposition, the nature of headlines, quotations, and images, and the placement and size of stories, this thesis argues, Canada's national newspapers privilege the circulation of dominant notions of "the enemy within," the axes of which are media(ted) discourses of "the Nation," "Muslims," "Immigrants," "Terrorism," and "Whiteness."
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    A quantitative analysis of the effects of feeding and daily variation on plasma acid-base status in resting horses
    (University of Guelph, ) Smithurst, Kerri Jo; Geor, Raymond J.; Lindinger, M.
    This thesis investigated the main acid-base constituents in equine plasma that exhibit daily variation. A major focus was to determine total carbon dioxide concentration ([TCO2]). Jugular venous blood was sampled every 1 to 2-h over 25-h from 10 resting and either fasted or fed Standardbreds on a 3-wk conditioning program and racehorse diet. The independent variables, strong ion difference ([SID]), total concentration of weak acids and bases ([Atot]), and partial pressure of carbon dioxide (PCO2), were assessed to determine factors affecting hydrogen ion concentration ([H +]) and calculated [TCO2] using the physicochemical approach to acid-base balance. Variations were found in [glucose], haematocrit (Hct), plasma proteins ([PP]), chloride ([Cl-]), bicarbonate ([HCO3-]), [H+], [SID], [A tot] and PCO2; all of which appeared to be due to effects of feeding or dehydration. Mean [TCO2] varied up to 10 mmol/L throughout the day and 70% of the horses had a calculated measurement above 36.0 mmol/L.