Researcher calls for ring rot test lab

Idaho currently ships potatoes east for testing

By JOHN O'CONNELL

Capital Press

Following a season in which bacterial ring rot resurfaced in Idaho's potato crop, a University of Idaho researcher hopes to establish the first in-state facility to test growers' samples for the disease.

U of I Extension potato seed pathologist Phil Nolte said a ring rot lab would require roughly a $35,000 investment for a polymerase chain reaction machine to perform DNA testing.

Idaho, the nation's largest commercial and seed potato production area, now ships samples east for ring rot testing. Nolte thinks a North American Free Trade Agreement-approved lab could be operational by next season. He may approach processors for financial assistance.

"When you consider what people have lost based on having bacterial ring rot in the fields, the amount of money we're talking is a drop in the bucket. When you're talking $35,000, some of these guys have lost millions this year," Nolte said.

He said the lab would help international seed exporters meet testing mandates, and domestic buyers make certain the seed they procure is clean. He said PCR machines can test up to 200 potato tissue samples at a time for about $40 per test.

"With six tests, you can run 1,200 tubers. If you get a zero on 1,200 tubers, you're looking at a very small amount of bacterial ring rot -- if it's there," Nolte said.

Seed certification relies on a visual inspection to detect signs of ring rot, such as wilting foliage and tubers with vascular ring discoloration or deterioration. But symptoms aren't always expressed, especially at high elevations.

"Probably 99 percent of the time, the seed grower wasn't aware it was in the seed because the seed grower and certification people didn't see it," Nolte said.

Nolte said his Idaho Falls laboratory and the Kimberly Research and Extension Center are good potential locations for a lab, which could also take samples from Washington and Oregon.

The U of I Aberdeen Research and Extension Center already has a PCR machine, used for testing of five disease pathogens.

Research technician Katie Fairchild explained tests take about a day to run. The machine works by heating samples to break DNA apart. A probe with DNA from a specific disease is inserted into the severed DNA and will bond with any matching DNA from the samples, indicated the presence of the disease.

North Dakota State University plant pathologist Neil Gudmestad developed the modern bacterial ring rot testing techniques and has been testing many samples from the flare-up in Idaho's current crop.

He plans to work with Nolte and a Washington State University bacteriologist to develop an in-season testing method using the petioles of potato leaves. With a petiole test, Nolte said growers could avoid storing infected spuds, and leaf samples used for winter potato virus Y seed lot tests could also catch ring rot in certification.

Gudmestad said ring rot flare-ups tend to be cyclical, occurring roughly every decade as growers become lax in sanitation procedures that prevent bacteria spread. Idaho's last flare-up was in 2002.