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ARS Home » Pacific West Area » Corvallis, Oregon » Forage Seed and Cereal Research » Research » Publications at this Location » Publication #323320

Research Project: Reducing the Impact of Diseases on Hop Production

Location: Forage Seed and Cereal Research

Title: Susceptibility of hop cultivars to downy mildew: associations with chemical characteristics and region of origin

Author
item Woods, Joanna - Oregon State University
item Gent, David - Dave

Submitted to: Plant Health Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/3/2016
Publication Date: 3/7/2016
Citation: Woods, J., Gent, D.H. 2016. Susceptibility of hop cultivars to downy mildew: associations with chemical characteristics and region of origin. Plant Health Progress. 17:42-48.

Interpretive Summary: Hop downy mildew is a yield limiting disease in many hop production regions of the world. In this research, various cultivars were evaluated for their susceptibility to downy mildew. There was a large range of downy mildew susceptibility and vigor amongst commercial cultivars, with some cultivars possessing a very high level of resistance. On whole, though, disease resistance and vigor was significantly greater in cultivars originating from Europe than those originating from the U.S., Japan, and Australia/New Zealand. Vigor was related to the levels of a chemical constitute in cones typically found in wild hops from North America. The generally poor vigor observed in cultivars derived outside of Europe likely is indicative of a lack of tolerance to the crown infection phase of the disease. Thus, the best sources of downy mildew seems to be found in cultivars from the United Kingdom and Europe, which are typically lower yielding and lack distinctive aroma and flavor characteristics presently desired by craft brewers. Improving resistance to the disease will be a long-term challenge.

Technical Abstract: Hop downy mildew is a yield limiting disease in many hop production regions of the world. In this research, 110 cultivars that are or were widely grown in the U.S., Europe, or Australasia were evaluated in western Oregon over three years for their reaction to the shoot infection phase of downy mildew and vigor. There was a large range of downy mildew susceptibility and vigor amongst commercial cultivars, with some cultivars possessing a very high level of resistance. On whole, though, disease resistance and vigor was significantly greater in cultivars originating from Europe than those originating from the U.S., Japan, and Australia/New Zealand. Amongst a subset of 79 cultivars, vigor was negatively correlated with cohumulone levels in cones, a chemical constitute of bittering acids typically found in germplasm derived from North America. The generally poor vigor observed in cultivars derived outside of Europe likely is indicative of a lack of tolerance to the crown infection phase of the disease. Thus, the best sources of downy mildew seems to be found in cultivars from the United Kingdom and Europe, which are typically lower yielding and lack distinctive aroma and flavor characteristics presently desired by craft brewers. Introgression of downy mildew resistance into North American germplasm with high yield and desirable brewing characteristics is needed.