Plant pathologist Barbara Christ has been selectively breeding potatoes for disease resistance and other traits for decades. She believes her research is on the verge of yielding potato plants that will not succumb to late blight.

Diseases such as the witch’s broom fungus can wipe out cocoa crops. That malady infects the plants, leaves, and stems so that the cocoa plant can’t grow. “For example, a few years ago a witch’s broom outbreak in Brazil wiped out production and had major social implications,”
Guiltinan says. “Because of the controversy over genetically modified foods, there are no GM cocoa plants, but we have worked with the breeders to develop disease-resistant cocoa plants through conventional breeding and sped up the process by using gene markers to isolate desired genes that carry disease resistance.”

Perhaps less exotic than cocoa research, but every bit as important, is research being done on potatoes by plant pathologist Barbara Christ. For more than two decades she has studied potato breeding and disease resistance, focusing on diseases such as early and late blight.

Late blight, which was responsible for the Great Irish Potato Famine of the 1840s, still ruins potato crops across the country. “Our mission is to develop potatoes that are adapted to Pennsylvania and have resistance to diseases,” Christ says. “If varieties are more resistant, growers can use less fungicide. Also, some diseases have no effective chemical control, so resistance is the only tool available.”

In conjunction with other breeders, Christ has co-released 11 new potato cultivars, which are now grown commercially on more than 18,000 acres across the Northeast. Currently, she is working with wild potato species that have tremendous disease resistance, looking for ways to transfer that resistance to standard varieties while retaining the standard varieties’ desirable characteristics. She oversees the growing of 180 varieties at Rock Springs.

Christ also conducts research on integrated pest management strategies. “Growers need new varieties, but developing a new cultivar can take 10 years,” she says. “They also need techniques they can use now. We can get results from IPM projects in a year or two, providing information that helps growers slow down diseases through cultural practices.”

About half of the potatoes grown in Pennsylvania are varieties used to make potato chips, and Christ’s work reflects that fact. “We work collaboratively with the chip companies, experimenting with a number of potato varieties,” she says. “We actually make chips. Our ‘chip lab’ is at the old mink farm at Rock Springs, where we use the same oils and temperatures
as the chip-making companies. Chipping potatoes are more dense and round and have a higher starch content than other varieties.”

To date, most of Christ’s potato-genetics work has been accomplished by traditional crossbreeding techniques, but in recent years she has employed gene markers for faster selection of desired traits. “DNA analysis reduces the time it would take to put materials in the field to see if we have disease resistance,” she says.

She believes her research is on the verge of yielding potato plants that will not succumb to late blight. “The resistance traits have been achieved for late blight,” she says. “Now the trick is to come up with varieties that are worthy of commercial cultivation.”

Faculty referenced in this article are John Carlson, associate professor of molecular genetics and director of the Schatz Center for Tree Molecular Genetics; Barbara Christ, professor and head of plant pathology; Surinder Chopra, assistant professor of maize genetics; Majid Foolad, professor of plant genetics; Henry Gerhold, professor of forest genetics; Mark Guiltinan, professor of plant molecular biology; Timothy McNellis, associate professor of plant pathology; and Kim Steiner, professor of forest biology.