September 15, 2005:
Cross-breeding commercial potatoes with wild species can enhance
the plants' fitness for organic farming, says University of Wisconsin-Madison
professor of plant pathology Doug Rouse.
Together with biology professor Shelly Jansky of UW-Stevens Point,
Rouse has leveraged the innate disease resistance of wild potatoes
to create hybrids which, to varying degrees, resist soft rot, common
scab, black scurf, early dying disease, and early blight.
There are “environmental and human health” disadvantages
to using the conventional fumigant that prevents early dying disease
(aka Verticillium wilt), Rouse wrote in a 2003 article
in the journal Plant Disease. The fumigant is caustic and
can burn unprotected skin. “It's a cyanide product…
it affects respiration and the heart,” Rouse explains, adding
that he is also concerned that the biocide may affect earthworms,
although he has not seen any research on the subject.
Even with “extensive use of pesticides,” Jansky and
Rouse wrote, “an estimated 22 percent of [worldwide] potato
yield is lost each year to diseases and pests.”
The genetic diversity of wild potatoes may provide an alternative
solution. According to the researchers, “Genes for resistance
to almost all major potato diseases” exist in wild varieties,
but “they have not been used widely in the development of
When comparing the hybrid potatoes with the popular varieties known
as Atlantic, Russet Burbank, and Russet Norkotah, Jansky and Rouse
found that all of the hybrids were more resistant than at least
one conventional variety for at least one type of disease.
The most promising new hybrid, called “C545,” showed
improved resistance to soft rot, scab, pitted scab, early dying
disease, and early blight.
“When you start with one of these wild [species]… you
may lose some of the size [and] appearance,” Rouse notes.
“We’re continuing to make crosses to try to get resistance
into plants that have large tubers.” The scientists say they
have not yet created a hybrid large and attractive enough to be
acceptable to consumers.
“We’re hoping to go after the actual genes,”
Rouse says enthusiastically. However, genetic engineering is not
in the works. Sexual hybridization, Jansky and Rouse wrote, is a
more appropriate technique for introducing a “broad spectrum”
of genetic changes in the plants.
“We’re making the material available to plant breeders,”
Rouse said. “The plant breeding program [at the University
of Idaho] has some materials that look pretty good.” He said
that many other plant breeders have been making crosses to develop
potatoes that are resistant to Verticillium wilt.
Katherine Friedrich is a graduate student at the University
of Wisconsin-Madison in Life Sciences Communication (formerly known
as Agricultural Journalism).