Paul Nicholson |
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Genetics and mechanisms of resistance to facultative pathogens of cereals I lead a group investigating facultative pathogens involved in disease complexes of the stem-base and ear of cereals. Emphasis is placed on study of the genetics and mechanisms of resistance to Fusarium species. Two forms of resistance have been proposed; Type I (resistance to initial infection) Type II (resistance to spread within the cereal head). While several sources of Type II resistance are known it has proved to be much more difficult to identify Type I resistance. We are developing methodologies to enable identification and characterising of Type I resistance. We are carrying out disease trials on populations produced with the above materials, combined with genetic mapping, to identify quantitative trait loci (QTL) associated with resistance. In addition, we are using the model plant species Arabidopsis thaliana to gain insight into potential signalling pathways important in host resistance. Results are translated into crop systems to determine whether these pathways also function in wheat and barley. This will provide candidate genes for exploitation by scientists and plant breeders. We are also investigating seedling and adult plant resistance to the stem-base disease eyespot, caused by two closely related species Oculimacula yallundae and O. acuformis. This work is combined with genetic mapping to produce markers suitable for use by plant breeders to follow resistance in their breeding programmes. Role of mycotoxins in pathogenicity Work is combined with study of the basis of pathogenicity of Fusarium species. The most important species infecting wheat and barley are F. graminearum and F. culmorum, both of which produce trichothecene mycotoxins. Isolates produce predominantly deoxynivalenol (DON) or nivalenol (NIV) and are differentiated on the basis of their chemotype. We are investigation the role of chemotype in host-pathogen interaction to establish the basis of the balanced selection that is maintaining both chemotypes in the population. Work also includes study of variability within fungi and the development and use of quantitative diagnostic assays to study host resistance, competition between fungal species and fungal pathogenicity. Temporal and spatial regulation of toxin biosynthesis during host colonisation is studied to determine the effect of host and environmental factors on toxin accumulation in plant tissues.
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