Grant pays for PVY testing
By JOHN O'CONNELL
The University of Idaho can continue testing Idaho potato seed lots for necrotic strains of potato virus Y for two more years, thanks to a recently awarded Specialty Crop Block Grant.
The testing effort received $155,442 from the Idaho State Department of Agriculture, which awarded about $893,000 for block grants from USDA.
The Idaho potato industry requires that the state's seed lots be planted in an annual winter grow-out in Brawley, Calif., where plants are evaluated for diseases and leaves are collected for enzyme-linked immunosorbent assay testing in the Idaho Crop Improvement Assocaition's Idaho Falls laboratory. Since 2010, additional samples from seed lots testing positive for PVY have been sent to U of I laboratories to determine the presence of necrotic PYV strains, which can rot tuber flesh.
Alex Karasev, an associate professor of plant virology, and U of I Extension seed potato pathologist Phil Nolte tested more than 1,500 samples from the most recent winter grow-out in their laboratories for necrotic strains. The grow-out included 800 seed lots.
Karasev believes the testing contributed to a 40 percent reduction in necrotic PVY strains from the previous year. He said the prevalence of the common PVY strains has also declined steadily since 2007, when Idaho implemented mandatory grow-out testing.
Karasev said PVY was a longstanding nuisance that emerged as a major threat to the potato industry in 2000, when necrotic strains that had troubled the European industry since the 1980s arrived here.
"The question is where they came from and how this happened. This is still an open question," Karasev said.
Idaho seed lots are restricted from selling any seed with more than 2 percent PVY. Though the seed certification program doesn't differentiate based on common or necrotic strains, Karasev and Nolte alert growers when they detect necrotic strains and advise strongly against replanting lots with any amount of necrotic PVY in order to produce more seed, a process known as re-certification.
"It's all done discretely," Karasev said.
In the most recent grow-out, 14.07 percent of lots had at least 2 percent PVY, down from 18.84 percent in the 2011 crop. U of I economists estimate every 1 percent of PVY in seed costs commercial growers $16-$!8 per acre in reduced yields.
Karasev explained necrosis surfaces mostly in fresh spud varieties, especially Yukon Gold, and aren't bad in Russets, though necrotic PVY strains can still reduce Russet yields.