Date of Award
2017
Publisher
North Dakota State University
Document Type
Thesis
Degree Awarded
Master of Science (MS)
Program
Plant Pathology
Department
Plant Pathology
College
Agriculture, Food Systems and Natural Resources
Faculty Advisor
Markell, Samuel G.
Description
Downy mildew, caused by Plasmopara halstedii (Farl.) Berl. and de Toni, is an economically important disease in cultivated sunflowers, Helianthus annuus L. The objectives of this study were to determine disease pressure in North Dakota and South Dakota, determine the virulence phenotypes in the pathogen population, determine the baseline sensitivity to azoxystrobin and evaluate select isolates for fungicide insensitivity. While downy mildew was present in many fields, incidence was typically low. To determine virulence phenotypes, selected isolates were evaluated on an expanded set of differential lines. New virulence was found to the Pl8 resistance gene, but no virulence was observed on the PlArg, Pl15, Pl17 and Pl18 genes. Using a discriminatory dose of 10 ug ai azoxystrobin/seed, no isolate approached infection levels found in inoculated, nontreated controls; therefore, the pathogen is considered sensitive to azoxystrobin in the greenhouse and azoxystrobin should still suppress downy mildew in the field.
Recommended Citation
Gilley, Michelle A., "Downy Mildew of Sunflowers: Establishment of Baseline Sensitivity to Azoxystrobin and Monitoring for the Development of Fungicide Resistance and Plasmopara Halstedii Virulence Phenotype Changes" (2017). Plant Pathology. 41.
https://digitalcommons.ndsu.edu/plant-path/41
Rights
NDSU policy 190.6.2
Rights Link
https://www.ndsu.edu/fileadmin/policy/190.pdf
Author ORCID Identifier
0000-0003-1486-3037
Handle Identifier
https://hdl.handle.net/10365/28688