Lewis, Mary C., Ph.D. (2011) The development of assays to determine the effect of environmental factors on the viability of Plasmodiophora brassicae resting spores. PhD thesis, University of Warwick.

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Abstract

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.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QK Botany S Agriculture > SB Plant culture
Library of Congress Subject Headings (LCSH):	Plasmodiophora brassicae, Clubfoot -- Environmental aspects
Official Date:	September 2011
Dates:	Date Event September 2011 Submitted
Institution:	University of Warwick
Theses Department:	School of Life Sciences
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Kennedy, Roy
Sponsors:	Great Britain. Agriculture and Horticulture Development Board
Extent:	xvii, 242 leaves : ill., charts
Language:	eng

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