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Date of Award
2016
Publisher
North Dakota State University
Document Type
Dissertation
Degree Awarded
Doctor of Philosophy (PhD)
Program
Plant Pathology
Department
Plant Pathology
College
Agriculture, Food Systems and Natural Resources
Faculty Advisor
Markell, Samuel G.
Description
Downy mildew (Plasmopara halstedii) and rust (Puccinia helianthi) are two economically important diseases of sunflower (Helianthus annuus) in North Dakota. Both diseases are capable of causing significant reductions in yield and quality. Effective disease management tools for both diseases are limited. Genetic resistance to both pathogens is frequently overcome by new pathogen races and only one efficacious fungicide is currently available to manage downy mildew. In order to identify additional management tools for downy mildew and rust, three research studies were done. The objective of the first study was to evaluate the efficacy of a novel fungicide, oxathiapiprolin, for the management of sunflower downy mildew. Seventeen inoculated field trials were conducted from 2011-2015 to test the efficacy of oxathiapiprolin. Results indicate that oxathiapiprolin significantly and consistently reduced downy mildew incidence and determined the optimal effective rate, which ranged from 9.37 – 18.75 µg active ingredient per seed. The second and third objectives focused on identifying accessions with novel sources of genetic resistance to P. halstedii and P. helianthi isolates collected in North Dakota. In the past, a disproportionate amount of resistance genes have been identified in wild Helianthus germplasm originating from Texas. For both studies, 182 wild H. annuus and 33 wild H. argophyllus accessions originating from Texas were obtained from the USDA North Central Regional Plant Introduction Station and screened to both pathogens in a greenhouse environment. Results from these individual studies identified numerous accessions with high levels of resistance to P. halstedii and P. helianthi, some accessions had high levels of resistance to both. Overall, results from these three studies will provide information and tools that will be useful for the long-term management of both diseases.
Recommended Citation
Humann, Ryan, "Development of Management Tools for Sunflower Downy Mildew (Plasmopara Halstedii) and Rust (Puccinia Helianthi)" (2016). Plant Pathology. 50.
https://digitalcommons.ndsu.edu/plant-path/50
Rights
NDSU policy 190.6.2
Rights Link
https://www.ndsu.edu/fileadmin/policy/190.pdf
Handle Identifier
http://hdl.handle.net/10365/25564