Hidden Elm Population May Hold Genes to Combat Dutch Elm Disease - Washington, DC

Hidden Elm Population May Hold Genes to Combat Dutch Elm Disease / March 30, 2011 / News from the USDA Agricultural Research Service

WASHINGTON—Two U.S. Department of Agriculture (USDA) scientists may have discovered "the map to El Dorado" for the American elm—a previously hidden population of elms that carry genes for resistance to Dutch elm disease. The disease kills individual branches and eventually the entire tree within one to several years.

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 USDA's Agricultural Research Service (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.