Hidden elm population may hold genes to combat Dutch elm disease

摘要

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.