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UBC Theses and Dissertations

Investigating the molecular mechanisms of Fusarium Head Blight resistance in wheat Foroud, Nora Afsaneh


Fusarium Head Blight is a disease of cereal crops caused by a group of trichothecene-producing Fusarium species. Two major forms of resistance to Fusarium Head Blight are Type I resistance (resistance to initial infection) and Type II resistance (resistance to disease spread). Using functional genomics approaches, the effect of FHB-elicitors on the defense response of three wheat genotypes that share the susceptible cv. 'Superb' pedigree were evaluated. Distinct differences were observed between the resistant genotypes and 'Superb', as well as between the Type I and Type II genotypes. The data presented in this thesis suggests that different molecular mechanisms exist not only between susceptibility and resistance responses, but also between different forms of genetic resistance. It is proposed here that Type I resistance involves a combination of structural features that slow fungal penetration and the activation of a systemic response in uninfected tissues adjacent to the site of infection to prevent and minimize secondary infection; whereas, Type II resistance is more likely a form of local resistance. Based on the results from the functional genomics study, follow up experiments where wheat heads were primed with FHB elictiors and subsequently inoculated with a virulent F. graminearum strain and evaluated for changes in disease outcomes, support the hypothesis that Type I resistance involves the activation of a systemic response. Furthermore, an analysis of the role of plant hormone signalling using a combination of genetic and biochemical analysis suggest that jasmonic acid signalling is involved in Fusarium Head Blight resistance.

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