WEST LAFAYETTE, Ind. - Researchers from Purdue and Colorado State universities have discovered that the fungus responsible for thousand cankers disease, a lethal affliction of walnut trees and related species, has a rich genetic diversity that may make the disease more difficult to control.
Adjunct assistant professor of forestry Keith Woeste and fellow researchers analyzed the genes of 209 samples of Geosmithia morbida from 17 regions of the U.S. to determine the genetic diversity of the fungus, its possible origin and how it spread throughout the West and to parts of the East.
The researchers identified 57 distinct haplotypes, or genetic races, among the samples, a curious finding for an organism that reproduces by cloning itself. The high diversity of Geosmithia morbida likely indicates that the fungus mutates readily, said Woeste, who is also a hardwood specialist with the U.S. Forest Service.
"The high mutability of this fungus means we can expect the unexpected," he said. "We can't count on the fungus' genes to be the same year after year, which certainly makes it harder to control. It will also be harder to breed trees resistant to this disease."
First reported in the early 1990s, thousand cankers disease is deadly to black walnut trees and their relatives, such as butternut and wingnut trees. Black walnut trees are prized for their dark, high-quality wood and play a valuable role in the forest ecosystem as a food source for wildlife.
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