Graduate Thesis Or Dissertation

 

Dynamics of Zymoseptoria tritici Fungicide Resistance in the Willamette Valley of Oregon Public Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/rf55zc31z

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  • The development of resistance to multiple fungicide classes is currently limiting disease management options for many pathogens, while the discovery of new fungicide classes has become less frequent. To address this pressing issue, a three-part study with different layers of complexity, objectives, and experimental approaches was conducted using the model fungicide resistance pathosystem: Zymoseptoria tritici. The virulence of azoxystrobin-resistant Zymoseptoria tritici was tested in greenhouse assays, and results indicated that azoxystrobin-resistant Z. tritici populations were less virulent. Results of a series of field inoculations with fungicide-resistant, fungicide-sensitive, and resistant/sensitive mixtures indicated that the competitive ability and fitness of azoxystrobin-resistant Z. tritici in vivo was influenced by environmental factors. A large-scale hierarchical survey of commercial wheat fields in the Willamette Valley of Oregon was executed to monitor seasonal changes and spatial variation of propiconazole- and azoxystrobin- resistant Z. tritici. An increase of azoxystrobin resistance was recorded over the two-year study. In contrast, propiconazole resistance stayed relatively stable over time. Both fungicide-resistant phenotypes were found to be spatially random, and the greatest amount of spatial variation occurred at the smallest hierarchical scale of the survey. Results of this research represent a broad effort to understand fitness trade-offs associated with mutations, as well as a more focused effort to understand local dynamics of Z. tritici fungicide resistance in the in the Willamette Valley of Oregon.
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