By MATEUSZ PERKOWSKI
Farmers in Oregon are trying to develop new disease-resistant hop varieties with a novel "pot-in-pot" system that allows for easier replacement and segregation of plants.
"This is the first time hops have been done this way, so we're still learning," said Fred Geschwill, grower who has the "pot-in-pot" facility installed at his farm in Woodburn, Ore.
The breeding program, funded by the Hop Research Council industry nonprofit, started with 80,000 hop plants that were inoculated with common fungal pathogens -- powdery mildew and downy mildew -- in a greenhouse.
Of that initial cohort, 6,000 plants were chosen to be planted in the pot-in-pot field, in which the hops grow in one container that sits within another container buried in the ground.
Keeping the hops in individual containers prevents the roots and vines from intertwining, which could result in misidentification, and also reduces the effort of replacing the old plants with new ones each year.
Generally, hops don't thrive in containers, but plants that show a resistance to the diseases will be planted in the ground at other cooperating farms for further evaluation, said Geschwill.
"More than one year, they will have to be in the field, but we will get rid of a lot of them," he said, noting that the 6,000 hops will likely be pared down to about 1,500 candidates for replanting.
John Henning, a USDA research geneticist who is assisting in the breeding program, said he doesn't expect the pot-in-pot system to negatively skew the results.
"If a plant's going to be vigorous in a pot, it will be vigorous in the field," he said.
The mix of plants currently being tested includes crosses that may replace the "Willamette" variety that has been popular in Oregon's Willamette Valley.
Henning is examining crosses of "super alpha" varieties used for imparting bitterness to beer, which are commonly grown in Washington, as well as crosses that look promising for craft brewing.
He has also created crosses from parent plants that seemed to demonstrate disease-resistant traits.
Hops at the pot-in-pot facility will not be treated with fungicides, and Henning will scour the field every couple of weeks to weed out plants that seem more susceptible to disease than others.
Since only female plants produce the hops that brewers need for beer production, males will also be removed from the field -- however, Henning plans to keep particularly healthy ones for breeding purposes.
It could take eight years to identify a new variety from among the seedlings that are being tested, and the plants will also be grown out in Washington and Idaho.
Brewers want hop farmers to use fewer chemical applications, but they would likely oppose genetic engineering that could speed the process, Henning said.
Even so, he expects genetic markers associated with disease resistance to aid in the conventional breeding program by making it easier to identify promising selections.
Resistance to downy mildew is associated with several hop genes, which makes it more complicated to breed for this trait than for resistance to powdery mildew, said Henning.
Downy mildew also has the potential to be more destructive for farmers in Oregon, as the disease can kill plants while powdery mildew is more likely to dent yields and quality, he said.
Growers are frequently confronted with weather that is conducive to these hop diseases -- downy mildew thrives in cool, moist conditions but powdery mildew prefers hot, dry conditions, Henning said.