RESEARCH UPDATE
Breeding a more sustainable potato
Wisconsin researchers focus on disease resistance and organic performance in potato varieties

By Katherine Friedrich

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).