Oat is an important crop for livestock feed and human food. Increased interest in the health promoting properties of oat has led to a need to explore diverse oat germplasm for improved nutritional quality. One target for improved nutritional quality could be an altered fatty acid composition. A study was conducted to explore the fatty acid profile of diverse accessions from the world oat collection preserved in the Canadian national seed genebank, Plant Gene Resources of Canada (PGRC), at the Agriculture and Agri-Food Canada (AAFC) Research Centre, Saskatoon, Saskatchewan, Canada and genotypes from the Crop Development Centre (CDC), University of Saskatchewan, Saskatoon and the Eastern Cereal and Oilseed Research Centre (ECORC), AAFC, Ottawa, Canada. Accessions included a wide range of Avena sativa L. and other selected species from the genus Avena (A. byzantina C. Koch, A. sterilis L., A. fatua L., A. sativa subsp. nudisativa (Husn.) Rod. et. Sold. and A. strigosa Schreb.). The fatty acid profiles of 917 oat accessions from these taxa were analyzed using gas chromatography, revealing significant variability for the three major fatty acids in oat oil. Oleic and linoleic acid demonstrated the greatest variation. A few A. sativa accessions had higher oleic and lower palmitic acid levels compared to the general average. Some hexaploid wild oat accessions (A. sterilis) showed relatively high oleic and below average levels of palmitic and linoleic acid compared to A. sativa. A. strigosa accessions had consistently higher levels of oleic acid than other Avena species. Based on initial results, 52 selected A. sativa accessions were grown in 2009 in replicated field trials and re-evaluated to gain insight into the influence of the growing environment on fatty acid composition. Fatty acid composition was affected by genotype, whereas location significantly affected palmitic and oleic acid content. Correlations were determined among the contents of the six fatty acids, oil content and protein content. Oleic acid content was positively correlated with oil content, which may be particularly important to plant breeders for nutritional quality improvement of future oat cultivars. The understanding gained from this research suggests the possibility of improving the fatty acid profile of future oat cultivars for food and feed.

Thesis (M.S.)--Auburn University, 2007. / Abstract. Includes bibliographic references.

Thesis (Ph. D.)--University of Adelaide, 1993. / Includes bibliographical references (leaves 203-220).

Thesis (Ph. D.)--University of Adelaide, Dept. of Crop Protection, 1996? / Includes bibliographical references (leaves 159-184).

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.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 182A-196). Also available via the Internet.

Most plant toxicology tests developed in support of environmental laws use a single stress applied to an individual plant. While tests using individual species or stresses require fewer resources and are easier to interpret, they are under increasing criticism for being unrealistic and missing important ecological interactions. The objective of this research was to increase our understanding of how plants and plant communities respond to a variety of stressors. Model plant communities of spring wheat (Triticum aestivum) and wild oats (Avena fatua) were planted at three densities and five proportions in the field. Puccinia recondita, the causal agent of wheat leaf rust, was inoculated on half of the plots. Disease severity was estimated as percent of wheat flag leaves covered by rust lesions. Plants were harvested at maturity and measured. Seeding density rarely had a significant influence on rust severity, probably because tiller density differed little as a result of compensation due to increased tillering at low seeding densities. In contrast, increasing the proportion of wheat in mixtures with wild oats consistently increased wheat leaf rust severity. There was no evidence to suggest that wild oats acted as a barrier to inoculum movement. Wild oats' effect on wheat leaf rust was probably through its competitive reduction of wheat tiller density. Both wheat and wild oats seed weight decreased as the proportion of wild oats increased in mixtures. This indicates that intraspecific competition was stronger in wild oats than was intraspecific competition with wheat in these mixtures. Wild oats generally did not respond to the presence of leaf rust on wheat, while wheat was negatively impacted. Thus, there was little competitive advantage to wild oats when its competitor (wheat) was diseased. A small subset of the field treatments was treated with ozone, because of the limited space available in the open-top ozone exposure chambers. Wheat height and aboveground biomass generally decreased with ozone exposure and with increasing disease severity in both years, while total grain weight decreased significantly only with disease and only in one year. There was no interaction between ozone and disease, regardless of cultivar, density, or plant response variable measured. There was little evidence that ozone exposure affected the severity of wheat leaf rust. In general, there seemed to be a lack of interactions among the different stressors and the results varied considerably depending on year and wheat cultivar. / Graduation date: 1998

Three experiments were conducted to investigate the effects of various cereal grain types on the production performance of dairy cattle and the colonization of <i>Clostridium perfringens</i> in the intestinal tract of cattle. The first experiment investigated the effect of feeding two different cultivars of barley (cv. Harrington and Valier) and two different cultivars oat (cv. Derby and AC Assiniboia) grain on feed intake, milk yield and milk constituents. It was found that barley or oat may both be successfully incorporated into the concentrate portion of western Canadian dairy rations. NRC Dairy 2001 predictions for both oat and barley diets very closely predicted dry matter intake and milk production. AC Assiniboia oat fed cows produced the lowest percentage of fat (P<0.05) compared to the other dietary treatments. Oat fed cows produced milk with lower total solids (P<0.05) than barley fed cows. Experiment two investigated the effect of replacing barley with corn in the concentrate of a dairy ration on performance parameters as well as fecal shedding of <i>C. perfringens</i>. Corn can successfully replace a portion of the cereal grain in a typical western Canadian dairy ration without adverse effects on milk production, feed intake and feed efficiency. Corn fed cows produced significantly higher milk protein than barley fed cows (P<0.05). Dairy NRC 2001 milk production predictions were similar to observed milk yields. Mean (±SEM) level of colonization (log cfu/g) of <i>C. perfringens</i> in the feces was lower (P<0.05) in barley-fed (1.30±0.27) compared with corn-fed (2.47±0.27) cows. Experiment three was a survey to determine the level of shedding of <i>C. perfringens</i> in feces of dairy cattle at different ages and stages of lactation and in feedlot cattle through the backgrounding and finishing phases. No relationship was found between heifer age and level of shedding or between days in lactation and level of shedding. Sixteen percent of the sampled cows exhibited high levels of shedding (3.02±.46) log cfu/g feces) through all stages of lactation without exhibiting adverse effects on health. No relationship was found between age of heifer and level of <i>C. perfringens</i> shedding in the feces. Steers shed significantly higher (P<0.05) levels of <i>C. perfringens</i> during the last phase of finishing compared with other feeding phases. Further research investigating <i>C. perfringens</i> colonization in cattle is required.

Three experiments were conducted to investigate the effects of various cereal grain types on the production performance of dairy cattle and the colonization of <i>Clostridium perfringens</i> in the intestinal tract of cattle. The first experiment investigated the effect of feeding two different cultivars of barley (cv. Harrington and Valier) and two different cultivars oat (cv. Derby and AC Assiniboia) grain on feed intake, milk yield and milk constituents. It was found that barley or oat may both be successfully incorporated into the concentrate portion of western Canadian dairy rations. NRC Dairy 2001 predictions for both oat and barley diets very closely predicted dry matter intake and milk production. AC Assiniboia oat fed cows produced the lowest percentage of fat (P<0.05) compared to the other dietary treatments. Oat fed cows produced milk with lower total solids (P<0.05) than barley fed cows. Experiment two investigated the effect of replacing barley with corn in the concentrate of a dairy ration on performance parameters as well as fecal shedding of <i>C. perfringens</i>. Corn can successfully replace a portion of the cereal grain in a typical western Canadian dairy ration without adverse effects on milk production, feed intake and feed efficiency. Corn fed cows produced significantly higher milk protein than barley fed cows (P<0.05). Dairy NRC 2001 milk production predictions were similar to observed milk yields. Mean (±SEM) level of colonization (log cfu/g) of <i>C. perfringens</i> in the feces was lower (P<0.05) in barley-fed (1.30±0.27) compared with corn-fed (2.47±0.27) cows. Experiment three was a survey to determine the level of shedding of <i>C. perfringens</i> in feces of dairy cattle at different ages and stages of lactation and in feedlot cattle through the backgrounding and finishing phases. No relationship was found between heifer age and level of shedding or between days in lactation and level of shedding. Sixteen percent of the sampled cows exhibited high levels of shedding (3.02±.46) log cfu/g feces) through all stages of lactation without exhibiting adverse effects on health. No relationship was found between age of heifer and level of <i>C. perfringens</i> shedding in the feces. Steers shed significantly higher (P<0.05) levels of <i>C. perfringens</i> during the last phase of finishing compared with other feeding phases. Further research investigating <i>C. perfringens</i> colonization in cattle is required.

Oat is known to synthesize several epoxy fatty acids in seeds using peroxygenase (PXG), a type of hydroperoxide-dependent epoxygenase. This thesis aims to molecularly clone and functionally characterize the PXG genes from oat developing seeds. The research started with identifying additional PXG genes from oat expressed sequence tag (EST) databases using a previously identified oat peroxygenase AsPXG1 as a query sequence. This resulted in the identification of six homologous contig sequences from the EST data bases. Of them, two contigs with high sequence similarity and alignment with plant PXG/caleosin proteins were selected for cloning and functional analysis. Rapid amplification of cDNA ends (RACE) and reverse transcriptase-polymerase chain reaction (RT-PCR) were used to retrieve the full length cDNAs of the contigs, which resulted in identification of three putative PXG genes, AsPXG2, AsPXG3 and AsPXG4. Open reading frame (ORF) of AsPXG2 is 702 bp long encoding a polypeptide of 233 amino acids, while ORFs of both AsPXG3 and AsPXG4 are 627 bp in length coding for 208 amino acids. All these putative peroxygenases comprise a single transmembrane domain, presumably for lipid droplet anchoring, conserved hisditine residues for heme-binding and a conserved EF-hand motif for calcium-binding. To functionally characterize the three genes, their ORFs were individually expressed in Escherichia coli/Pichia pastoris. The enzymatic assays showed that all transformants produced 9,10-epoxystearic acid methyl ester in the presence of oleic acid methyl ester and cumene hydroperoxide, indicating all three genes encode functional peroxygenase. AsPXG3 has the highest specific activity at 42 mol/mg/min with about 25% substrate conversion efficiency. Substrate specificity assays on free fatty acids showed that AsPXG3 could epoxidize all mono- and poly-unsaturated fatty acids tested, with linolenic acid (C18:3-9c,12c,15c) being the most preferred substrate. Site-directed mutagenesis of three conserved histidines and nine conserved residues surrounding the histidines in AsPXG3 showed that substitution of the first conserved histidine at position 32 (H1) and the third conserved histidine at position 102 (H3) with alanine respectively resulted in complete loss of the enzymatic activity, while substitution of the second conserved histidine at position 98 (H2) resulted in only slight reduction of the activity, indicating that only H1 and H3 are absolutely essential and probably involved in heme-binding for the peroxygenase. Substitution of leucine at position 29 (M1), isoleucine at position 97 (M5), and lysine at position 101 (M8) with alanine reduced the enzymatic activity on oleic acid methyl ester by more than 80% relative to the wild type enzyme, indicating these three residues are also very important for catalytic activity. The activity of M1, M5 and M8 mutants was also drastically reduced on all other free mono-unsaturated fatty acids tested (>60%). However, to linolenic acid, M5 showed only slight reduction of the activity (~15%) and M8 even increased the activity by 12% relative to the wild type enzyme. These results suggest that these conserved residues might play roles in defining the shape and size of the catalytic site for interaction of the heme with fatty acid substrates.