UT Grows Disease-Resistant Dogwoods

KNOXVILLE — University of Tennessee researchers have developed four dogwood trees that are highly resistant to two diseases which have devastated the species in recent years.

Three scientists with the UT Agricultural Experiment Station have successfully cultivated a variety they call Appalachian Spring that is highly resistant to dogwood anthracnose, a disease that kills trees by affecting the foliage and bark.

“Appalachian Spring is the only cultivar that has data to substantiate its anthracnose resistance,” said Dr. Mark Windham, who developed the variety from a single disease-free tree found near Camp David at Catoctin Mountain Park in Maryland. “This dogwood is not the product of breeding; we discovered it growing amid thousands of other trees that had died of anthracnose.”

Windham said Appalachian Spring has gone through rigorous double-blind tests that confirmed it is disease-resistant. The variety has been licensed to Tennessee Advanced Genetics, a firm that will market the variety when sufficient supplies have been grown to meet market needs, he said.

UT tree specialists expect the cultivar to rejuvenate the state’s dogwood nursery industry, which has been hurt by anthracnose. Tennessee growers supply more than 70 percent of the dogwoods sold commercially in the United States.

Windham and Drs. Robert Trigiano and Will Witte are also preparing to patent three dogwood varieties that are not killed by powdery mildew, a disease that stunts the growth of trees. While anthracnose kills trees at higher elevations and in shaded environments, powdery mildew can strike dogwoods in any environment, Windham said.

The three have named the mildew-resistant plants Karen’s Appalachian Blush, Jean’s Appalachian Snow and Kay’s Appalachian Mist, after their wives. Windham said that any future dogwood cultivars developed at UT would have the general name “Appalachian.”

Windham and his colleagues grafted cuttings from the naturally disease-resistant trees onto the rootstock of other dogwoods. Neither anthracnose nor powdery mildew attacks the roots of dogwood trees, Windham said. The trio will continue research into crossbreeding the varieties in search of a tree that resists both diseases.

The dogwood is important from more than its aesthetic values, Windham said. Dogwood berries are an important source of food for birds and other wildlife, and the leaves add calcium to forest soil.

Windham said the UT Agricultural Experiment Station continues the search for naturally disease-resistant trees and solicits information from the public about wild dogwoods that are growing successfully at higher elevations and in shaded environments. UT has established a Web site for its dogwood research: http://dogwood.ag.utk.edu/

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