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The soil inhabiting organism Plasmodiophora brassicae infects brassica crops causing millions of pounds of damage each year. The result of infection is extensive galling of the root system and eventually plant death. Current control measures are limited and the variability of the pathogen and its lifecycle makes finding new controls difficult. It was therefore considered that if several measures could be identified which reduced P. brassicae infection then they could be used in combination, reducing the possibility that the pathogen could evolve to overcome the controls. This research therefore aimed to find a set of control measures, and where possible a mode of action, which could be used in combination or alone to reduce P. brassicae infections. Calcium nitrate was identified as an effective control measure which affected several stages of P. brassicaes lifecycle (Fig :1) as well as the predominant pathogen race. The type of growth medium used was also found to affect the extent of infection and to influence the pathogen population. Soils from two areas were identified as suppressive to P. brassicae and the nature of their suppression was determined to be due to both biotic and abiotic factors. The identification of these suppressive soils may lead to the development of a bio-control or it may be possible to encourage these soils to develop in other areas. Some more "holistic" control measures were also investigated. Applications of calcified seaweed were found to be at least as effective in decreasing clubbing as calcium carbonate. Applications of chitin and seaweed extract however were found to have no effect on P. brassicae infection in this instance. The research within this thesis has identified several control measures and answered some questions about P. brassicae. It has however, also raised more questions and identified areas which require more research.

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Concerns about Vermont‘s dairy farm viability, greenhouse gas emissions, and reliance on fossil fuels have prompted growing interest in the production of biodiesel and oilseed meal from Vermont-grown oilseed crops. The idea is that Vermont farmers could grow and harvest oilseed crops; the seed or beans could be pressed into vegetable oil and oilseed meal; and the oil could be processed into biodiesel, thereby producing both liquid biofuel and protein meal for livestock from Vermont crops. Results from this study indicate that oil, meal, and biodiesel production from sunflowers grown in Vermont is technically feasible, and may be economically feasible at both the farm and commercial scales, depending on scale and market conditions. Farmers, entrepreneurs, and policymakers are intrigued by the potential to decrease Vermont‘s dependency on imported fuels and feed, reduce farms‘ production costs, realize local economic benefits from import substitution, and lower greenhouse gas emissions. Despite the promise of ―Vermont-made‖ biodiesel and oilseed meal, however, it remains largely an unproven concept. Production of oilseed crops is relatively rare in Vermont, especially in quantities sufficient for biodiesel or livestock meal production. The equipment, capital, acreage, and expertise needed to successfully grow, harvest, and process these crops have not been identified, and the economic feasibility, optimal scale, and environmental and macroeconomic impacts of these new enterprises in Vermont is unknown. This study investigates the technical and economic feasibility of producing biodiesel and livestock feed from Vermont oilseeds at a farm scale and a commercial scale. Technical feasibility at the farm scale is assessed using data from two Vermont farms. Enterprise budgets are used to assess the economic feasibility and profitability of the crop, oil and meal, and biodiesel enterprises individually and as a whole under two sets of market conditions. Economic feasibility and environmental and economic impacts of a commercial-scale biodiesel facility in Vermont are assessed using a simulation model. None of the farm-scale enterprises were profitable as budgeted in this analysis, although the commercial-scale plant was more profitable as crude oil prices rose. The most promising enterprise at the farm scale appears to be oil and meal production. This study prompts additional questions regarding the extent to which Vermont crop production should shift to include oilseeds for biodiesel production, the net energy return to the farm, and lifecycle greenhouse gas emissions from on-farm production.

M. Tech. (Biotechnology, Department of Biosciences, Faculty of Applied and Computer Sciences) Vaal University of Technology / Sweetpotato is one of the most important food crops in developing countries including South Africa. Currently two major types of cultivars are grown in South Africa: one is the orange-fleshed sweetpotato (OFSP) which has high β-carotene content, a precursor of vitamin A. The second type is the cream-fleshed sweetpotato (CFSP) which has low β-carotene content but is high in dry matter. Most South Africans prefer the CFSP although the OFSP offers more advantages. This presents a challenge to plant breeders to develop new varieties that will combine the desirable qualities of both the cultivars. To achieve this goal, plant breeders need knowledge about the genetic variation of the crop to develop an efficient breeding programme. This study assessed the genetic relationships of 28 orange- and cream-fleshed sweetpotato accessions by (i) examining the variation in leaf proteins, (ii) using random amplified polymorphic DNA (RAPD) and, (iii) using variation of the ITS region. The analysis of proteins, RAPD and variation of the ITS region polymorphism levels were 55.6%, 98% and 16.5%, respectively. Dendrograms generated from all the analyses generally clustered the accession according to their flesh colour and country of origin. Analysis of molecular variance (AMOVA) found a significant difference between OFSP and CFSP and a significant difference between the South African and non-South African germplasm. The high genetic diversity in the South African sweetpotato germplasm is a positive indicator for a breeding programme that has a number of targets such as breeding for nutritional improvement, disease resistance and drought tolerance / Hub and Spokes and National Research Foundation (NRF)

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Typescript. / Digitized by Kansas Correctional Industries

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1988. / Vita. Abstract. Includes bibliographical references (leaves 82-84). Also available via the Internet.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2007. / Title from title screen (site viewed Dec. 4, 2007). PDF text: xi, 134 p. : ill. ; 6 Mb. UMI publication number: AAT 3271926. Includes bibliographical references. Also available in microfilm and microfiche formats.

A procedure for model-assisted climate impact assessment is developed. The approach combines data from observations and atmospheric general circulation models (GCNs), and provides the basis for a potentially valuable means of using information derived from GCMs for climate impact assessments on local scales. The first component of this procedure is an extension of the 'climate inverse' method of Kim al. (1984). Daily mesoscale temperature and precipitation values are stochastically specifed on the basis of observational data representing the average over an area corresponding to a GCN grid element. Synthetic local data sets generated in this manner resemble the corresponding observations with respect to various spatial and temporal statistical measures. A method for extrapolation to grid-scale 'scenarios' of a changed climate on the basis of control and experimental integrations of a GCM, in conjunction with observational data, is also presented. The statistical characteristics of daily time series from each of these data sources are portrayed in terms of the parameters of a multivariate time-domain stochastic model. Significant differences between the model data sets are applied to the corresponding parameters derived from the observations, and synthetic data Bets representing the inferred changed climate are generated using Monte-Carlo simulations. The use of the procedure is illustrated in a case study. The potential climatic impacts of a doubling of atmospheric carbon dioxide concentrations on three important North American grain cropping regions is investigated using two 'physiological' crop models. Although the specific results must be interpreted with caution, they are moderately optimistic and demonstrate possible means by which agricultural production may adapt to climatic changes. / Graduation date: 1987