Second chance for the American elm
« on: 2010-06-18 16:52:20 »
I am one of those that clearly remember these beautiful trees and was convinced for the longest time that somehow I had brought the fungus back from my Grandfather green houses in Germany. I watched them slowly die and lay barren many a majestic landscape in Ontario.
All but wiped out by Dutch elm disease, the stately giant may yet make a comeback thanks to researchers at the University of Guelph
Source: The Globe and Mail
Author: Martin Mittelstaedt
Date: Thursday, Jun. 17, 2010
The American elm was once among the most beloved and recognizable of trees, a stately giant whose towering height and cathedral-like canopy of leaves made it a favourite to line city streets across North America.
But the elms, which once numbered in the tens of millions, have become an arboreal rarity, all but wiped out in the United States and Eastern Canada in the 1960s and ’70s, the victim of an inadvertently imported fungus to which they had little resistance.
Now, scientific help is on the way, thanks to efforts by biologists at the University of Guelph to create trees resistant to the fungus, known as Dutch elm disease.
The recovery effort, involving advanced plant cloning techniques, could yield trees ready for planting in as little as three to five years, and help re-establish a species that has been driven to the brink of extirpation in many areas, according to those involved in the research.
“What we’re saying is we’re going to do our best to make this happen,” said Praveen Saxena, a plant biologist at the university who is heading the elm program.
Researchers are collecting leaf, twig and root cell samples from some of the one in 100,000 elms that seem to have some natural ability to resist the fungus. A few such trees have already been catalogued by researchers at the university, but they’re on the lookout for more, such as surviving specimens in people’s backyards, Dr. Saxena said.
“People are very interested, especially people who had seen the beauty of elms and then have seen them dying,” he said.
The elm cells will be cultured in the laboratory, developed into clones and exposed to the fungus. The cells that survive direct contact with their adversary will be grown into trees, and then further tested for resistance.
If the research yields viable trees, it will be a scientific advance that could help other threatened plants, including American chestnuts and butternuts, two formerly widespread trees that have also been devastated by fungal diseases to which they have little resistance.
The fungus that kills elms originated in Asia and was identified scientifically in the Netherlands, which is why it is named Dutch elm disease. In North America it was first detected around 1930 in Ohio, where elm logs carrying the fungus had been imported from Europe for making furniture. Despite efforts at the time to prevent it from spreading, the fungus quickly became established in the United States and Canada and is now impossible to eradicate.
In Canada, elms remain common on the Prairies, although these trees aren’t resistant to the disease and may be surviving only because spores from the fungus haven’t reached sufficient concentrations to destroy them. In a worrisome sign, Winnipeg, with an estimated 160,000 elms, is losing them to the disease at the rate of 40,000 each decade, according to city figures.
It is often possible to help individual trees survive using pesticides, or by the prompt removal of infected trees. But these actions are costly and only slow the spread of the disease.
The cloning technology used in the Guelph research has been around for years, but there was little funding available to see if it could help the elms. The $400,000 cost is being covered by a private family charity, the Gosling Foundation.
“There is a lot of emotional connection with these trees,” said Susan Gosling, co-founder of the foundation. “They are stately and elegant and so beautiful.”