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 current
cultivars.”
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).
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