Golden Nematodes Are Anything But
ARS nematologist Bill Brodie (left) and Cornell University plant breeder Robert
Plaisted assess the merits of new nematode-resistant varieties.
Just as all that glitters is not necessarily gold, all that's golden is not
necessarily goodas any long-time potato farmer on New York's Long Island
That's because a Hicksville, Long Island, potato farm was unhappily the
setting in 1941 of the United States' first known infestation of the golden
nematode, Globodera rostochiensis. The tiny worm's enormous appetite for
potato plant roots can wipe out entire crops.
To make matters worse, each female nematode can produce hundreds of eggs
capable of lying dormant in the soil for decades, just waiting for the right
soil conditions and a vulnerable potato crop.
Bill B. Brodie cant do anything about soil conditions, but he's spent
more than a quarter of a century steering potato producers away from the second
half of the nematodes wish listvulnerable potato varieties.
A plant pathologist in ARS' Plant Protection Research Unit at Ithaca, New
York, Brodie's collaborated there with Cornell University researchers Robert L.
Plaisted, Edward D. Jones, Donald E. Halseth, Steven A. Slack, and H. David
Thurston on nonchemical control strategies to defeat the golden nematode.
The ARS-Cornell team has developed nematode-resistant potato varieties, as
well as a crop rotation plan to stymie the pest and halt its spread. Since
1966, scientists with USDA and Cornell and other universities have brought
forth 31 potato varieties that resist golden nematode attacks. Among them is
the ARS-bred Atlantic, a leading chipping potato and the country's most widely
grown nematode-resistant potato.
"The first 40 years of golden nematode control depended on fumigating
infested fields with as much as 90 gallons per acre of chemicals," Brodie
"During the years when the greatest number of golden nematode-infested
fields were being found, federal regulatory agencies spent more than $2 million
annually to survey the soil for nematodes and for other activities. And the
State of New York was spending more than $250,000 a year for the soil fumigants
to treat infested fields."
Chemical use against the pests came to a halt after traces of the chemicals
were detected in Long Island groundwater in the early 1980's. To fill the
protection gap, Brodie and colleagues provided convincing evidence that 2
consecutive years of growing a nematode-resistant variety of potato controlled
the pest as effectively as the chemicals.
Besides, fumigants wouldn't wipe out all the live nematode eggs lurking in
the soil, Brodie notes. But, resistant potato varieties' roots naturally fend
off nematode infection, starving the hatching nematodes and slashing nematode
totals by about 90 percent each year.
The watershed event in the war against the golden nematode was the 1954
discovery of a single gene whose presence could gird potatoes against the
pests attacks. That gene, called H-1, was the cornerstone of the first
nematode-resistant potato varietiesCornell's Peconic in 1966, and ARS'
own Wauseon, released at Beltsville, Maryland, in 1967.
But growers beyond nematode-besieged Long Island were slow to trade in their
favorite spuds for an unfamiliar, though resistant line, Brodie recalls.
"In 1944, New York State quarantined portions of Nassau and Suffolk
Counties on Long Island where the nematode was first found. Then, in 1969, the
federal government again quarantined portions of those countiesplus
Steuben County in New York and New Castle County in Delaware, where the
nematode had also been discovered," says Brodie.
"Because those quarantine measures prevented the spread of golden
nematodes, growers outside those areas never experienced any losses to the
nematode and they weren't interested in switching varieties."
But, as the years passed, science and market demands finally converged, with
development of resistant varieties such as Atlantic, Allegheny, and Kanona that
combine nematode-blocking ability with the quality traits growers demand.
"Potato breeders throughout the United States need parent plants to
make crosses," Brodie explains. "They've begun using resistant
varieties as parents because these potatoes happen to have other traits that
they like. Last year, I found three newly released potato varieties that no one
even knew were resistant,"
In a stroke of scientific serendipity, the ARS-Cornell team's persistent
pursuit of better nematode-fighting tubers has put them ahead in a contest they
didnt know they'd entered.
"There are five races of golden nematodes around the world, but in this
country we'd always had just one of those races, Ro1," Brodie reports.
Then, in 1994, we found a race of golden nematodes on our experimental
farm that was increasing, instead of decreasing, on our resistant varieties!
Tests showed we now had race Ro2 of the golden nematodes in the United
Fortunately for American potato farmers, Brodie and the Cornell researchers
had, for the past decade, kept the fire going under a small project on
pinpointing potato lines that would also resist exotic races of golden
nematoderaces other than their longstanding enemy, Ro1.
"Bob Plaisted and I knew that we'd been relying too much on the H-1
gene for our nematode resistance. So we had begun developing different
germplasm here and sending it to Peru for testing, since they have other races
of the golden nematode there." Brodie explains. "Our objective was to
develop germplasm that would be resistant to the other races and also adapted
to our growing conditions in the United States.
"We had some germplasm that was really good at resisting several races
of the golden nematode, and we thought we'd simply make it available to other
countries that already had those races," says Brodie.
"But call it chance, or serendipity, or whateverwhen we were
developing germplasm with resistance to exotic races, some of that same
germplasm showed resistance to Ro2, as well. Since we had incorporated
resistance to Ro1 into this germplasm, we're more than 5 years closer to having
a potato variety that's resistant to both races and ready for release to
growers. So this little project has turned out to be a good value for our
Studies are under way at Cornell University to pinpoint the basis of the new
germplasm's resistance to Ro2. "We don't know if it's one gene, like the
H-1 gene, or several." Brodie says.
Meanwhile, he continues to check all the new varieties from potato breeding
programs at Cornell, the Universities of Maine and Minnesota, Agriculture
Canada, and Frito Lay, Inc.as well as ARS potato breeding programs at
Beltsville, Maryland, and Aberdeen, Idahoin search of fresh weapons
against the golden nematode.
"We consider the golden nematode the most serious pest threatening the
U.S. potato industry," Brodie concludes. "Federal, state, and local
governments have come together on this program to protect our potato
crop." By Sandy Miller Hays, ARS.
Genetic Resources Unit, Cornell University, Ithaca, NY
"Golden Nematodes Are Anything But" was published in the
issue of Agricultural Research magazine.