Many of the nations elm trees were done in by Dutch elm disease, a fungal disease introuced into this country in 1931. Their stately branches once lined many a city street.
Plant breeders have been trying to develop resistant strains, but without much luck.
Today, the U.S. Department of Agriculture announced that its scientists had discovered a previously hidden population of elms that carry genetic material resistant to the disease.
According to a press release from the Agricultural Research Service: "It has been accepted for 80 years that American elms (Ulmus americana) are tetraploids, trees with four copies of each chromosome. But there have also been persistent but dismissed rumors of trees that had fewer copies—triploids, which have three copies of chromosomes, or diploids, which have two copies.
"Now botanist Alan T. Whittemore and geneticist Richard T. Olsen with the ARS have proven beyond question that diploid American elms exist as a subset of elms in the wild. Their findings will be published in the April edition of the American Journal of Botany. Whittemore and Olsen work at the U.S. National Arboretum operated by ARS in Washington, D.C."
Meanwhile, on a more romantic note, the U.S. Forest Service has launched an online system for reporting the location of American elm tree "survivors." In the first few weeks of the program, people have in five states have logged the locations of more than 40 trees.
Northern Research Station researchers Jim Slavicek and Kathleen Knight have heard many reports of big elm trees, but these reports have been light on directions. “People are always happy to report seeing an American elm,” Knight said in a press release. “When they see a big elm, they remember it, but they don’t always remember the location well enough to share their discovery.”
According to the service, identifying American elm trees resistant to the disease across their natural range would allow researchers to create a genetically diverse elm seed plantation.
The on-line system can be found at: http://nrs.fs.fed.us/SurvivorElms
Once people log the location, they're asked to describe the tree and what kind of habitat it's in. Slavicek and Knight are looking for American elm trees that are 24 inches or greater in diameter at chest height (about 4.5 feet), and that show no signs of the disease. That's because only big trees are old enough to have been exposed to the disease, so only those can be considered “survivor” American elms, according to Knight.
For forest service said that, ultimately, Slavicek and Knight want to visit locations reported through the website and collect a branch to propagate in a nursery. Once big enough, the tree will be injected with Dutch elm disease to determine whether it really is disease tolerant. If so, it will be cross-pollinated with healthy American elms and the seedlings will be used in forest restoration, the service said.