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ARS Home » Pacific West Area » Corvallis, Oregon » Forage Seed and Cereal Research Unit » Research » Publications at this Location » Publication #411474
Research Project: Development of Superior Hops and Resilient Hop Production Systems

Location: Forage Seed and Cereal Research Unit

Title: Seven publicly available hop genotypes with multi-race powdery mildew resistance

Author
item Altendorf, Kayla
item Woods, Patrick
item Heineck, Garett
item RICHARDSON, BRIONA - Oregon State University
item KENNY, STEVE - Yakima Valley Community College
item Gent, David

Submitted to: Journal of Plant Registrations
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/8/2025
Publication Date: 11/4/2025
Citation: Altendorf, K.R., Woods, P.O., Heineck, G.C., Richardson, B.J., Kenny, S., Gent, D.H. 2025. Seven publicly available hop genotypes with multi-race powdery mildew resistance. Journal of Plant Registrations. 19(3). Article e70035. https://doi.org/10.1002/plr2.70035.
DOI: https://doi.org/10.1002/plr2.70035

Interpretive Summary: Powdery mildew is a fungal disease of hop and can result in yield loss and reductions in quality. The pathogen that causes the disease exists in multiple forms and is known to overcome host plant resistance. USDA-ARS recently acquired a large collection of hop plants from a former Washington State University breeding program. The program had a long history of selecting for resistance in a region with high incidence of the disease. One hundred and two hop lines were surveyed to identify potentially novel sources of resistance. Of the 102, seven were resistant to all known forms in the Pacific Northwest growing region of the U.S. and two from Europe. Two of the seven were resistant to all known forms of the pathogen in the U.S. and Europe. The seven lines are now made publicly available through a germplasm release and can be acquired from the USDA National Plant Germplasm System for use in breeding and research.

Technical Abstract: Resistance to powdery mildew (caused by Podosphaera macularis) is primary objective for hop (Humulus lupulus L.) breeding programs. However, selection efforts are challenged by the existence of multiple races and the pathogen’s demonstrated ability to overcome host resistance. The need for novel sources of resistance and the recent material transfer of an extensive collection of hop germplasm from Washington State University to the USDA-ARS inspired an elimination screen of 102 hop genotypes to six races of the pathogen. Thirteen genotypes (12.7% of the collection) were resistant to the three races currently widespread in the Pacific Northwest, U.S. After inoculation with two additional races with novel virulence from Europe, seven (6.8%) were resistant. Of these, two (1.9%) were resistant to a third race from Europe. Of the group of seven resistant genotypes, one was already publicly available, and the remaining six are presented here and available from the USDA-ARS National Clonal Germplasm Repository (PI nos. 706212-706217). The lines can be used in breeding and to further research into the genetic mechanisms underlying multi-race powdery mildew resistance in hop.