PVY strain spreads through NW; website lets farmers follow research, learn more

By JOHN O'CONNELL

Capital Press

A worrisome tuber necrotic strain of Potato virus Y, called NTN, is now present in Idaho, Washington, Oregon and Montana, according to results of the 2011 Washington Commercial Seed Lot Trial.

"All four Pacific Northwest states had PVY NTN isolates present in their seed system, which is not a good sign. This is something that needs to be addressed," said Alexander Karasev, a University of Idaho associate professor of plant virology, adding the trial produced the first evidence he's seen of NTN in Oregon.

To educate growers on PVY and other new hybrid strains, a website has been launched by the USDA, the University of Idaho, Cornell University and the University of Wisconsin. At www.potatovirus.com, growers can read PVY research updates by experts from the three universities, along with related links and a discussion forum.

While the traditional strain hurts yields by damaging leaves and stunting growth, many strains that began surfacing in the U.S. in 2000 can impair tubers. Though it's widespread in Europe, Karasev said NTN represented a handful of samples in the Washington trial.

"The reason for this test in the Washington trials was to identify these lots where NTN may occur. The idea is you can probably get rid of NTN once you identify the source," Karasev said.

University of Idaho Extension seed potato specialist Phil Nolte added, "There's a lot of features about these new strains of PVY that aren't well understood yet, and what we're attempting to do is study all aspects of the disease problem."

The website is part of a multi-state PVY research program funded with a five-year, $2.38 million grant. The site indicates PVY has re-emerged in the U.S. due to the acceptance of varieties that don't express foliar symptoms, making detection more difficult, and the displacement of ordinary strains by hybridized and necrotic strains.

Using 2010 and 2011 test plot data, U of I agricultural economist Chris McIntosh estimated each percent of traditional PVY in Russet Burbank causes a 1.6 hundredweight mean yield reduction per acre, equating to an $8.23 loss at fresh market prices. The mean loss is $8.05 per acre in Russet Norkotah. He plans future research involving tuber necrotic strains.

In 2007, Idaho began laboratory testing leaves of plants grown in winter test plots to better detect PVY in seed. As a result, Nolte said the percentage of lots with at least one infected plant dropped from 60 percent five years ago to 40 percent in 2010, and the percentage of seed ineligible for recertification dropped from 27 percent to 8 percent. The 2011 winter tests should be completed by Feb. 17.

Jonathan Whitworth, an Aberdeen USDA ARS researcher, said a national survey finished in 2006 showed 40 percent of PVY strains were hybridized or necrotic.

Whitworth has worked on developing resistant potato varieties, including Premier Russet.

The website lists resistant varieties. It also recommends growers plant only certified seed and take measures to control aphids for protection from PVY.