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How What We Don’t Know Affects Our Ability to Prepare for Future Climates

Posted by Sonia A. Hall | May 24, 2022

Q&A with Aroma Hops Breeder Dr. Shaun Townsend

This article is part of a series where we share insights from conversations that I had with public plant breeders across the Pacific Northwest about their breeding programs and how climate change considerations intersect with their work. Through these conversations, I wanted to better understand the complexities of the plant breeders’ world, where there are elements that already provide useful information about adapting to future climates, and where there are questions—about the climate in the future, or the plants’ responses, or production, market, or other factors affecting a particular crops’ future—that intersect or even overshadow questions about how to prepare for future climates.

Hop plant with stunted leaves and stems.
Hop plant infected by downy mildew, a “tough nut to crack” for breeding tolerance to diseases. Photo: Shaun Townsend.

Maintaining yields under stressful climate-driven conditions is important in Oregon State University’s aroma hop breeding program, as in most breeding programs. However, two other aspects drive the work of Dr. Shaun Townsend, Associate Professor, Crop and Soil Science at Oregon State University. The first is how warmer (and maybe drier) springs could, maybe, help reduce the impacts of downy mildew, a “tough nut to crack” for breeding tolerance to diseases. Before I discuss my second take-away (it is about beer), see what Dr. Townsend had to say about breeding aroma hops for future climates:


Sonia A. Hall (SAH): Please describe the focus of your breeding program.

Dr. Shaun Townsend (ST): The OSU aroma hops program is a joint project between Indie Hops, a Portland-based hop merchant, and Oregon State University. I am the technical lead for OSU on this project. My task is to develop new aroma hop cultivars suitable for the craft beer industry and adapted to Oregon’s Willamette Valley. Although my target is western Oregon, these cultivars may also be grown in other Pacific Northwest hop-producing areas.

The Hop Growers of America 2021 Statistical Report lists the 2021 production at 116.5 million pounds (valued at more than $661 million) on 62,529 ac with most of that acreage (98%) being in Washington, Idaho, and Oregon. The United States leads the world in hop acreage and production. Our hops and hop products (pellets, etc) are shipped domestically and internationally.

SAH: Do you currently integrate climate change considerations into your breeding program? How? Are there conditions that make it hard, or unnecessary, to integrate climate change considerations into breeding?

ST: In short, yes, I integrate climate change considerations. Most of the reports that I have seen suggest Oregon will have warmer winters, more extreme heat waves in the summer, reduced winter snowpack which, in turn, reduces stream flow thus impacting summer irrigation. Summer wildfires and spring flood events could also become more prevalent. With this in mind, years ago I began selecting for drought tolerance in our breeding populations to address the potential disruption to summer irrigation in the future. When we’ve had an unusually warm winter, I’ve recorded those genotypes and genetic lines that grow vigorously in early spring with the assumption that they do not need the typical cold, wet winter to break dormancy. During last summer’s intense heat wave, we also recorded those genotypes that seemed to withstand the elevated temperatures. The overall goal with these efforts is to enhance the genetic potential of our breeding populations to respond to future climate-related threats.

Left photo shows flooded soil with regularly spaced out hop bines rising out of the water. Right photo shows long bines arrayed in rows, blurred by smoky air
Wildfires and floods are expected to become more prevalent in some areas as the climate changes, affecting many crops, including aroma hops. Photos: Shaun Townsend.

SAH: What traits or characteristics do you focus on in your current breeding program? Do those traits or characteristics confer the ability to adapt to future climates, that could be warmer in all seasons, with increasing variability and extremes? Or could they be affected by changing climates?

ST: I focus on the usual suspects for Oregon, including yield potential, downy and powdery mildew resistance, aphid, mite, and looper resistance, coning habit (that is, the distribution of cones on the plant), and maturity date. I’m not aware of these traits being directly associated with climatic factors like heat tolerance, but they would certainly help the plant withstand some of the consequences. For example, I would expect insect populations to possibly be higher or perhaps a greater diversity of pests to be present with warmer winters so incorporating general pest resistance would help plants cope with this potential stress.

SAH: What trade-offs do you consider, or would you need to consider, in breeding for warmer conditions, longer frost-free periods, and likely wetter springs and winters, drier summers, and a shift in the availability of irrigation water to earlier in the year (as expected in much of the Pacific Northwest?

ST: One way to address these conditions would be to develop earlier maturing genotypes that can take advantage of this shift in irrigation water, and possibly avoid smoke-filled days like we had after Labor Day in 2020. The potential disadvantage would be a possible yield reduction due to a slightly shorter growing season. Typically, the early-maturing hop cultivars do not yield quite as well as later-maturing cultivars.

SAH: Are there resources—online tools, Extension or other publications, events, etc.—that you know of that can help agricultural professionals integrate climate change into their work assisting producers with variety choice? Or any resources you wish existed?

ST: Not to my knowledge but this would be nice to have!


Large area covered in green hop cones.
Hops drying, in preparation for future use in brewing beer. Photo: Oregon Department of Agriculture.

As we discussed wish lists, we came to what’s unique about aroma hops: beyond yield, beyond tolerance to diseases or climatic stresses, the sensory profile of aroma hops, and how that translates to specialty beers, is key. And unfortunately, how changes in the profiles of essential oils in hops impact flavor and aroma in the resulting beer (let alone how changes in agronomic practices and climatic and biological stresses affect these profiles) is extraordinarily complex, interrelated, and not yet well understood. If it were, it would open many doors, including to managing hops to influence flavor and aroma under “normal” conditions or, more importantly for this article, explore what impacts future heat stress, warm winters, or late-season droughts could have on flavor and aroma profiles. This is what it will take to breed aroma hops for the future, as their future depends on brewery—and beer consumers’—acceptance. Hats off to chemists, brewers, plant breeders and others working to tease out how it all works together.

This article is also posted on AgClimate.net.

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