Field strains, W x R hybrids and inter-specific hybrids of the eyespot pathogen <I>Pseudocercosporella herpotrichoides </I>were characterised using traditional morphological and more recently developed molecular identification techniques which distinguished between the W and R pathotypes. The pathogenicity of these strains and hybrids to wheat, barley and rye was determined and related to their morphological and molecular characterisation and highlighted the unreliability of some of these techniques. Characterisation of the hybrids revealed the genetic inheritance from the parental strains which generally was greater from the R-type parent with some W x R- hybrids showing an intermediate morphology and others showing novel pathogenicity. An examination of the ability of the strains and hybrids to produce infection plaques <I>in vitro</I> found that infection plaque production could be related to the strain/hybrid pathogenicity on wheat, barley and rye. This indicates a requirement of infection plaques for successful host colonisation. No evidence was found of secondary metabolites produced in fungal culture filtrates using a wheat cell suspension assay and a wheat root inhibition assay which were involved in pathogenicity or host symptom induction. In a comparative study over time on wheat and rye, the development of visual disease symptoms was related to microscopic infection structures and the amount of fungal DNA present in the stem base. This revealed different infection strategies of the W and R pathotypes, the W-types being 'slow and stead' and the R-types being 'fast and furious' in their infection. The infection structures of both W and R-types were found to be always in advance of visual disease symptoms and limited colonisation of the host could occur without visual disease symptoms being present.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:660542 |
| Date | January 1999 |
| Creators | Perry, Kathryn Elaine |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/11880 |
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