ARS Scientists Settle Spud Debate
By Jan Suszkiw
January 31, 2008
The potato, a South American native,
was first exported outside its native home to Europe in 1567. From there it was
spread worldwide, but is still referred to by some today as the
In South America, native landrace potatoes grow in two general
areas: lowland southern Chile and in the Andes mountains from Venezuela to
northern Argentina. Debate has long focused on which of the two areas was the
source of the European potato. The Chilean source was proposed by Russian
scientists in 1929 and the Andean source sometime later by English researchers.
The latter hypothesis predominates today and is widely held.
Now, two "genetic sleuths" with the Agricultural Research Service
(ARS)graduate student Mercedes Ames
Spoonerhave clarified the issue by examining DNA from pressed plant
(or herbarium) specimens collected as early as 1700.
The English researchers' hypothesis contends Chilean spuds were imported as
insurance against late-blight disease epidemics of the 1840s, which devastated
the potato in Europe. But questions lingered. So, Ames and Spooner extracted,
sequenced and analyzed DNA samples from historical potato herbarium specimens
representing the early 1700s to 1910.
Vegetable Crops Research Unit in Madison, Wis., they checked for a specific
molecular marker that nearly completely distinguishes native Chilean from
Andean potatoes today and offers an accurate way to differentiate the two and
delineate their place in history.
In short, the English researchers were half right, note Ames and Spooner in
the February issue of the American Journal
of Botany. While the genetic makeup of today's European potato is
indeed Chilean, the landrace was introduced to Europe 34 years before late
blight first struck. It's possible European farmers then valued Chilean
potatoes for other traits, like optimal tuber development under long-daylight
The ARS finding will necessitate revising historical textbooks on the role
of late blight in the history of the European potato, as Chilean potatoes were
introduced long before the 1840s and persisted long after the
introduction of this disease into Europe. Practical implications include a
better understanding of the genetic makeup of modern potato cultivars.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.