Genetic roots: Scientists to examine DNA of George Washington’s trees

MOUNT VERNON, Va. – DNA collected from 13 trees at Mount Vernon, planted under George Washington’s supervision, is the first step in the creation of a genetic database for specific ornamental trees.

While the human genome has been detailed in a worldwide effort by thousands of scientists, nothing similar has been done with trees, noted J. Dean Norton, director of horticulture at Mount Vernon.

Genetic roots. Norton has enlisted the aid of Virginia Tech and the USDA Forest Service’s National Forest Genetic Electrophoresis Laboratory in Placerville, Calif., to use the Washington trees as the beginning of in-depth research into the genetics of a number of important tree species.

“This will be the start of a genetic database of these trees,” said Norton. “George Washington was always experimenting, trying new ways of growing his crops. I think it’s great that this 18th century site can still take the lead in research.”

Tree species. The 13 Washington Trees, the only trees now living that are known to have been planted at Washington’s direction, are seven American Holly, one Canadian Hemlock, two Tulip Poplar, two White Ash, and one White Mulberry.

Samples collected from 17 other trees of the same species at Mount Vernon and the surrounding area will also be evaluated in the project.

Norton contacted M.A. Saghai Maroof, a plant geneticist at Virginia Tech and an expert in the analysis of the DNA of plants, to help with the project.

“The genetic structure of plants are similar, but there are unique challenges in working with different types of plants,” said Saghai Maroof. “My expertise is in discovering genes that provide disease resistance in agricultural crops. For this project, it was important to bring in a laboratory with the capacity and the expertise to deal with the DNA of trees.”

DNA profiling. For that help, Maroof contacted the Forest Service laboratory.

Valerie Hipkins, director of the National Forest Genetic Electrophoresis Laboratory, said she was excited to be involved in the Washington Trees project.

“This facility provides molecular genetic information for the evaluation and protection of the genetic resource represented by our nation’s trees,” she said. “We will be doing DNA ‘profiling,’ which will be similar to the type of work most people are familiar with in criminal cases, or paternity cases, and the like.

“With people there is a tremendous database of information, so we are able to match DNA to an individual with a great degree of accuracy. There is no similar database for trees. We’ll be breaking new ground.”

The first collection of cutting by horticulturists from Mount Vernon was in February while the trees were in a dormant stage. Additional cuttings will be collected in the late spring or summer when the deciduous trees are in leaf.

The cuttings will be express-shipped to the Forest Service laboratory in California, where scientists will immediately begin the process of extracting DNA for detailed analysis.

Those findings will be important to Norton not just because of their intrinsic scientific value. Being able to identify individual trees – especially the Washington Trees – solves another problem for him.

Old age creeping in. Those 13 historically important trees are nearing the ends of their normal expected life spans. Last summer, cuttings were taken for rooting, and buds gathered for grafting from the trees to produce genetically identical clones.

Once those duplicates are established, Mount Vernon will be able to plant them on the estate, preserving them for future use on the grounds and for other horticultural endeavors.

The genetic profiles determined by the Forest Service’s laboratory will be used to authenticate clones of these historically important individual trees, ensuring they will be recognized and protected in the future, Norton said.

He acknowledges that the eventual establishment of a database of genetic information may have a broader significance in the conservation of trees in the future. In this, the Washington trees will play an important role.

“What better trees to serve as the foundation of this database,” he asked. “This type of genetic research is the path to the future. Who better to lead the way than the father of our country, George Washington?”