Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2001. / Härtill 4 uppsatser.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1975. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Graduation date: 1993

Fusarium oxysporum grown on natural media was believed not to produce mycotoxins of the trichothecene family. Using a defined chemical medium toxin production was investigated for and it was found that trichothecenes were produced. A yeast bioassay using Kluyveromyces fragilis, an organiam sensitive to such trichothecenes as T-2 toxin and verrucarin, was used for detection of toxin in culture filtrates. Detectable levels of toxin (0.2 $ mu$g in litre of culture) were seen by day 4 and peaked around day 9 corresponding to maximum growth (measured by mycelial mass). After this time fluctuations in the level of toxin and growth became evident, suggesting a breakdown of the toxins by the organism for a carbon source. Search for an enzyme or enzyme system, capable of degrading T-2 toxin in snail gut enzyme digested F. oxysporum, was attempted using the esterase substrate para-nitrophenol acetate. Esterase activity was detected in all fractions including culture filtrate, soluble protein fraction and insoluble protein fraction, as well as solubilized insoluble proteins (digested by contents of the crude extract). The soluble protein fraction exhibited the highest level of activity. Cells digested with the detergent Lubrol followed by precipitation of the solubilized proteins with ammonium sulphate revealed the presence of an active component(s) in the high molecular weight portion of the soluble cell fraction collected at 50 and 75% saturation. Further purification by DEAE-sepharose failed to produce an active component.

(+)-(2R,3R)-1,1,4,4-Tetraphenylbutane-1,2,3,4-tetraol (TETROL) and its derivatives were reacted with varying molar ratios of titanium isopropoxide (2:1, 1:1 and 1:2 tetraol:titanium isopropoxide) in an attempt to prepare potential titanium-based tetraol catalysts for enantioselective transformations. In each case, infrared and HNMR spectra suggested that the product was formed. We tentatively proposed that the structure of the catalyst was a spiro-type, but we could not determine conclusively what its exact structure was, despite using numerous techniques at our disposal (molecular modelling calculations, H NMR and IR spectroscopy, thermal analyses, powder diffraction, and single crystal X-ray diffraction). The catalyst and derivatives thereof were able to act catalytically for the enantioselective additions of diethylzinc compounds to aldehydes. The effects of temperature and solvent were investigated, and toluene and -78 °C were selected as optimal from the results obtained. (The reaction could, however, not be maintained at this low temperature for extended periods due to the fact that we did not have, at our disposal, the correct equipment. Each 16 h reaction was thus allowed to reach room temperature in each case.) The selectivity for the product 1-phenylpropan-1-ol (when benzaldehyde was the starting aldehyde) varied depending on the nature of the aryl substituents of the titanium-based catalyst. Using 0.2 molar equivalents of the chiral titanates, the highest selectivity was 42 percent (e.e.), but only when excess Ti(O-i-Pr)4 had been added to the reaction mixture. This was achieved with the tetra(ortho-methoxyphenyl)-TETROLate derivative. TETROL and its derivatives were also successful in metal-free catalysis where higher conversions and selectivities were observed, compared to when these were complexed to titanium. The highest selectivity was 70 percent (e.e.), achieved with the tetra(ortho-methylphenyl)TETROL derivative.

No description available.

Fusarium head blight (FHB) continues to threaten the economic sustainability of wheat and barley production in Canada and worldwide. The overall goal of this thesis is to expand our current knowledge of the FHB pathogen, Fusarium graminearum and its trichothecene chemotype diversity. Continuous monitoring of trichothecene chemotypes may well inform on the potential risk and the type of Fusarium populations present in a given region. Fusarium populations in Winnipeg and Carman, Manitoba were examined using chemotype as a marker in the field. Rapid expansion of the 3-acetyldeoxynivalenol (3-ADON) chemotype was observed in Winnipeg and Carman. 3-ADON chemotype is consistently found at high frequencies over the previously common 15-acetyldeoxynivalenol (15-ADON) chemotype, suggesting that the shift in pathogen populations is continuing. This study provides the first evidence on the presence of nivalenol (NIV) producing F. cerealis strains in winter wheat in Manitoba, Canada. Therefore, discovery of NIV producing F. cerealis in wheat poses a serious concern for the wheat industry in Canada. Phylogenetic, chemotypic, phenotypic, and pathogenic abilities of 150 strains of F. graminearum species complex (FGSC) from eight countries were investigated. Type and amount of trichothecenes produced by a strain are key factors in determining the level of aggressiveness of that strain regardless of its species origin. The sequence variations of TRI8 gene in different species in the FGSC were examined as Fusarium species may produce different types of trichothecenes depending on differences in the core trichothecene (TRI) cluster genes. The TRI8 haplotypes did group according to chemotype rather than by species, indicating that 3-ADON, 15-ADON and NIV chemotypes have a single evolutionary origin. Comparison of TRI gene expression demonstrated that accumulation of TRI transcripts was higher in 3-ADON producing strains compared to 15-ADON and NIV strains. The presence of masked mycotoxins deoxynivalenol-3-glucoside (D3G) in food and feed is an increasing concern. Canadian spring wheat cultivars inoculated with different chemotypes produce D3G upon Fusarium infection and moderately resistant/intermediate cultivars showed higher D3G/DON ratio compared to susceptible cultivars. / October 2016

Thesis (Ph. D.)--Swedish University of Agricultural Sciences, 2001. / Includes bibliographical references.

There is growing interest in malting and brewing with rye. However, previous research has shown a propensity for the development of deoxynivalenol (DON) in rye malts, even when levels on the grain is low. The main objective of this study was to assess the growth of F. graminearum and development of trichothecenes during malting of rye. Infected samples were obtained from 2016 variety trails in Minnesota. While DON levels were generally below 0.2 mg/kg, an average increase of 41 % was seen after malting. The most significant increases in DON were at three days of germination. Fusarium Tri5 DNA levels were observed to increase at two days. When single kernels were tested, most were free from DON. Levels in the bulk grain sample were due to a small number of highly contaminated kernels. In the malted samples, a greater portion of kernels contained DON, and overall levels were much higher.

Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 5 uppsatser.