Twenty-five years ago, the North Carolina Fraser fir represented less than one percent of all Christmas trees in the United States.

Today, the Fraser fir is a popular Christmas tree in North America — so popular that it has been chosen to decorate the White House more times than any other species.

But the Fraser fir has recently been at the mercy of a fatal fungus — Phytophthora root rot — that infects and destroys the root system of the tree. Almost nine percent of all Christmas trees grown in North Carolina are lost to the disease, research indicates, resulting in millions of dollars in losses.

To remedy the problem, NC State researchers Dr. John Frampton, associate professor of forestry and Christmas tree geneticist, and Dr. Eric Hinesley, professor of horticultural science, have developed a grafting procedure that joins Fraser fir shoots to the rootstock of disease-resistant trees. The procedure has shown promising results in testing, with more than 90 percent success rates in greenhouse testing and success rates anywhere from 60 to 100 percent when transplanted into the ground.

"We thought," Hinesley said, "if we can take a Fraser fir, a tree that's the whole package — pretty, soft, with a nice fragrance — and graft it to a rootstock that is resistant to Phytophthora root rot, we might be able to reclaim some of the lost land."

Phytophthora root rot tends to get started in areas where drainage is poor — at the bottom of hills or places that stay consistently wet. It is spread by contaminated soil, infected plants and flowing water that contains fungus spores. Once Phytophthora root rot infects the soil, it is almost impossible to eliminate, researchers say.

The first sign of Phytophthora root rot is a change in the needle color at the base of the tree from a verdant green to a rusty red. Eventually the needles on the Fraser fir wilt and the tree dies.

To test the new grafting procedure, the NC State researchers had to first determine the resistance of several fir species to the disease. In laboratory greenhouse experiments, fir species were found to range from very susceptible to Phytophthora root rot to almost completely resistant. Momi, Turkish, Korean, Canaan and Nordmann firs all appear to have some resistance to the disease, the researchers say. All would make a good replacement to the Fraser fir except the momi fir, an undesirable yellow-green tree with sharp needles.

Other species of fir have distinct advantages over the Fraser fir in that they are more tolerant of a higher temperature during the growing season. Fraser firs grow naturally on isolated mountaintops in western N.C. at elevations above 4,500 feet, yet most Christmas tree farms are located at much lower elevations. Grafting, researchers say, might allow Christmas tree growers to plant trees in North Carolina's Piedmont region, where most Fraser firs traditionally have trouble surviving.

Researchers tested newly grafted trees at NC State's Lake Wheeler Research Lab in Raleigh and the Upper Mountain Research Station in Laurel Springs, N.C. The trees were also tested in the mountains of Alleghany County, N.C.

In the greenhouses, the grafted trees' survival rates ranged from 93 to 98 percent, with the exception of the momi fir, which survived only 83 percent of the time. When transplanted into the land, survival rates were highest for the momi fir (80 to 100 percent), Nordmann fir (60 to 96 percent) and the Turkish fir (73 to 100 percent).

The study confirms that grafting can be accomplished successfully, researchers say, providing much needed hope for those who might otherwise be forced to abandon their tree farms due to the devastating effects of the disease.

Posted December 17, 2002

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