Potatoes infected with late
blight are shrunken on the
outside, corky and rotted
What's a potato's number-one enemy?
Anywhere on our planet the likely answer is: late blight. But tomorrow's
tubers may be safeguarded against this disease, thanks to research by
ARS scientists from coast to coast.
The researchers intend to develop hardy, highly productive potato plants
that not only produce top-quality potatoes but also shrug off attack
by Phytophthora infestans, the fungus-like microbe that causes
late blight. The disease, which led to the Irish potato famine of the
1840s, costs about $400 million in losses each year in the United States,
where potatoes are our favorite veggie.
An ARS team at the Western Regional Research Center in Albany, California,
has found and copied a gene that may work in concert with other genes
to fend off late blight.
They've named the gene Sbul, for Solanum bulbocastanum,
a late-blight-resistant species of wild potato that grows in Mexico.
This discovery followed up on pioneering research over the past decade
by plant physiologist John P. Helgeson, formerly with ARS in Madison,
Wisconsin. He fused S. bulbocastanum with the familiar domesticated
potato, S. tuberosum, creating unique hybrids that he offered
to researchers such as pathologist Dennis L. Corsini and geneticist
Joseph J. Pavek.
Corsini and Pavek, then with ARS in Idaho and now retired, crossed
the Wisconsin hybrids with other potatoes, then provided samplesvarying
in their resistance to late blightto other investigators. Each
cross had lessened the amount of genetic material from the wild potato.
This narrowed the California team's search for the resistance gene and
proved faster than trying to tease out the gene directly from the wild
Plant molecular biologist Teruko Oosumi, working with a group led by
ARS plant physiologist William R. Belknap at Albany, isolated and cloned
the Sbul1 gene from one of the Aberdeen hybrids. Then, Belknap,
microbiologist David R. Rockhold, and plant molecular biologist Malendia
Maccree moved the gene into domesticated S. tuberosum potatoes
for tests in the specialized greenhouses of plant pathologist Kenneth
L. Deahl in Beltsville, Maryland.
The California group also determined the blueprint, or structure, of
the Sbul1 gene and pinned down its location within the wild potato's
genome. To do that, Belknap used a portable, compact "library"
of all the genes in S. bulbocastanum, provided by Jiming Jiang,
professor of horticulture at the University of Wisconsin, Madison.
In Deahl's greenhouse research, the test tubers from Albany that had
the newly added Sbul1 gene showed resistance to the disease.
Now, additional tests, conducted in Michigan by David Douches, plant
and soil sciences professor at Michigan State University, East Lansing,
will reveal how well Sbul1-equipped potatoes perform outdoors
when exposed to the microbe. These field experiments should bring scientists
a step closer to determining whether genes from a wild, south-of-the-border
potato can protect its northern cousins from being battered by late
Wood, Agricultural Research Service Information Staff.
This research is part of Plant, Microbial, and Insect Genetic Resources,
Genomics, and Genetic Improvement, an ARS National Program (#301) described
on the World Wide Web at www.nps.ars.usda.gov.
William R. Belknap is in the
Improvement and Utilization Research Unit, Western Regional Research
Center, 800 Buchanan St., Albany, CA 94710; phone (510) 559-6072,
fax (510) 559-5818.
"Wild Potato's Genes May Blunt Late Blight" was published
in the August
2004 issue of Agricultural Research magazine.