Zachary James Ittel (he/him/his)
Graduate Student
North Dakota State University
Fargo, North Dakota, United States
Brandt Berghuis
University of Wisconsin River Falls
River Falls, Wisconsin, United States
Jessica Scherer, MS
Research Manager
North Dakota State University
Fargo, North Dakota, United States
Kaylie Schlecht
North Dakota State University
Fargo, North Dakota, United States
Robert Harveson, PhD
Professor
Department of Plant Pathology, University of Nebraska-Lincoln, Scottsbluff, NE 69361
Scottsbluff, Nebraska, United States
Febina Mathew, PhD
Associate Professor
Department of Plant Pathology, North Dakota State University, Fargo, ND 58102
Fargo, North Dakota, United States
Brent Hulke
USDA-ARS Sunflower Research Unit
Fargo, North Dakota, United States
Bryan Hansen
Research Specialist
North Dakota State University
Fargo, ND, USA
Samuel Markell, PhD
Professor
Department of Plant Pathology, North Dakota State University, Fargo, ND 58102
Fargo, North Dakota, United States
Sunflower rust, caused by Puccinia helianthi Schwein., is the most economically-important foliar disease of sunflower (Helianthus annuus). The disease is most effectively managed by genetic resistance, but new virulence phenotypes (races) can quickly render resistance genes ineffective. Since the most recent P. helianthi race survey, multiple new resistance genes have been identified and are thought to be deployed in commercially produced hybrids, making previous race information antiquated and the historical ‘standard international’ differential set outdated. The objectives of this study are to determine the prevalence of sunflower rust, modernize the differential set to reflect new resistance genes, and determine races of P. helianthi. In 2023 and 2024, prevalence of sunflower rust was determined across 102 surveyed-fields in the Northern Great Plains of the United States. When the disease was found, leaves with urediniospores were collected, single-pustule derived pathogen isolates were generated and increased in a greenhouse environment. Prevalence data and additional infected-plant samples were received from cooperators and single-pustule derived isolates were generated. Prevalence of rust in commercial fields was 98% (100/102). Races of select P. helianthi isolates are being determined using the standard nine-line differential set plus six additional proposed differentials. This study provides critical prevalence and virulence information that will inform management and breeding decisions that help prevent and/or mitigate losses to sunflower rust in the future.