[ti:Researchers Hope to Bring Back American Chestnuts]
[al:Science & Technology]
[ar:VOA]
[dt:2024-12-24]
[by:www.voase.cn]
[00:09.50]"Chestnuts roasting on an open fire,Jack Frost nipping at your nose..."
[00:23.56]This classic song written by Bob Wells and Mel Tormé in 1944 has long brought to mind the image of Christmas for generations of Americans.
[00:41.29]At one time, the American Chestnut was among the most common and largest trees in the eastern United States. 
[00:53.58]The wood was used to cover the walls of homes and schools. 
[01:00.98]The leaves helped add nutrients to the soil.
[01:05.61]And men on street corners sold chestnuts cooked on open fire.
[01:13.45]However, in the late 19th century, some East Asian varieties of chestnut trees brought to the U.S. carried a fungus that killed almost all American chestnuts.
[01:30.19]The American Chestnut Foundation (TACF) is a non-profit organization based in the eastern state of North Carolina.
[01:45.35]It has been working with researchers for over 30 years to bring the trees back to eastern U.S. forests.
[01:57.04]American chestnuts now exist mostly as huge root systems that grow into small trees. 
[02:07.47]The fungus harms them when the small trees start to develop fully.
[02:15.26]East Asian varieties, like those that brought the fungus in the first place, are resistant to the fungus.
[02:26.33]Researchers have tried to save American chestnuts by cross-breeding, or mixing, them with one kind of Chinese chestnut that can fight off the fungus.
[02:43.16]Progress has been slow, however. The trees the researchers have grown could not resist the fungus well enough to become large and healthy trees.
[02:57.52]That is why scientists are now trying to combine two methods: 
[03:04.84]cross-breeding and genetically modifying, or changing, the genes of American chestnut trees.
[03:14.44]They hope this will improve the tree's ability to resist attack from the fungus.
[03:22.06]But, progress was delayed by a recent mix-up involving two varieties of genetically modified American chestnuts. 
[03:35.12]Scientists at the State University of New York (SUNY) had hoped to get approval for the new seed this year.
[03:47.48]A changing climate and warmer temperatures may also make restoring the chestnut difficult in some areas.
[03:56.52]A team at Virginia Tech University published a study this summer about this issue. 
[04:04.87]They looked at projected future climates and then measured the shortest distance the trees would have to move to survive well in a new climate.
[04:19.61]For now, researchers know their work might not be successful in their lifetimes. 
[04:27.94]The process has been slow. And two of the first chestnut restoration experts, Bill Powell and Chuck Maynard, both died in the past 13 months.
[04:45.31]Linda McGuigan helped support Powell's and Maynard's research for years at SUNY's College of Environmental Science and Forestry.
[04:56.76]"The project moves on, lives on. And we honor their memory," McGuigan said. 
[05:05.25]"I want to do something good for the future, for my children."
[05:10.82]I'm Andrew Smith.