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Title: The development of assays to determine the effect of environmental factors on the viability of Plasmodiophora brassicae resting spores
Author: Lewis, Mary C.
ISNI:       0000 0004 2724 3862
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2011
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Clubroot disease, caused by the soil borne microorganism, Plasmodiophora brassicae is a significant disease of cruciferous crops as it results in stunted plant growth and reduced yield. The aim of this thesis was to investigate the effect of environmental factors on the viability of P. brassicae resting spores. Methods of detecting and quantifying the organism were optimised, and several different methodologies were investigated as potential bases for a viability assay. A molecular based seedling assay which quantified the rate of germination and subsequent root infection was determined to be an effective assay system. Investigation of several factors within a laboratory setting demonstrated that calcium stimulated the germination of resting spores, but subsequently reduced the level of infection in Brassica root tissue. Magnesium displayed the same effects but was not as significant as calcium. Ammonium displayed the same effects as calcium and magnesium however the level of ammonium applied was also significant. The commonly reported occurrence of lower incidence of clubroot disease at high pH was supported by finding less spore germination at high pH. Temperature was significant to P. brassicae spore germination and subsequent root infection, with the optimum temperature for germination and infection combined being 18.5-19oC. Low temperature (5oC) reduced spore germination but did not have a significant effect on the zoospores infective capability following germination. Prediction of environmental conditions within field settings was achieved using a simulation model specifically designed to incorporate parameters anticipated to influence P. brassicae viability. Monitoring the DNA equivalent levels of P. brassicae spores in soils over the course of crop growth allowed determination of predictive significant factors, and the results from these investigations supported the findings of the seedling assay. Calcium, magnesium, nitrogen and pH were among the factors significant to the level of P. brassicae spores within the soil.
Supervisor: Not available Sponsor: Great Britain. Agriculture and Horticulture Development Board
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QK Botany ; SB Plant culture