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“These look like corpses.” In the middle of a research farm in Virginia, in the east of the United States, Vasiliy Lakoba points to stunted bushes: the American chestnut, a species destroyed…
“These look like corpses.” In the middle of a research farm in Virginia, in the eastern United States, Vasiliy Lakoba points to stunted bushes: American chestnut trees, a species destroyed in the last century by a devastating fungus.
“The American chestnut was of great importance within the ecosystems of eastern North America before it was decimated by disease,” explains the director of research for the American Chestnut Foundation (ACF), which has worked since the 1980s to revive the species. .
Once an emblematic tree of the East Coast, the American chestnut was used as much for its wood as for its fruit, by man and beast.
But a fungus identified in 1904 at the Bronx Zoo in New York, on a tree from Japan, spread quickly and, in less than three decades, signed the death warrant for millions of chestnut trees.
“The destruction was so fast,” Vasiliy Lakoba told AFP, referring to “ghost forests.”
Today, only a few rare specimens still survive to adulthood in the wild.
“high and fair”
Located in the Appalachian Mountains, ACF’s main laboratory farm covers 36 acres and has tens of thousands of trees.
“It’s like picking apples, but with thorns…” laughs Jim Tolton, a farm technician, during a day of chestnut harvesting in early October.
The insects are collected using a crane, before the fruits are removed from them in a shed to be studied and used for future plants.
Before the disease, the American chestnut “grows tall and straight through the forest, fighting for light,” says Vassiliy Lakoba.
But with the arrival of the plague, a tree sees cancer appearing in its branches: a necrotic ulcer also called “tree cancer.”
It will then fight the disease by growing other branches here and there, giving it a bushy appearance, rather than the straight shape it once had.
No cure has yet been found to stop the spread.
Crossbreeding and transgenic
Imparting blight resistance to American chestnut is precisely ACF’s mission.
For this, two main avenues of research are explored: the first, implemented for years, consists of crossing an American chestnut with other species already resistant to the fungus, such as the Chinese chestnut.
The goal, after many crosses over several years, is to obtain an American chestnut that is also resistant, while retaining as much of the original genetic characteristics as possible.
“One of the drawbacks” with these crosses, Vasiliy Lakoba explains, “is that disease resistance turned out to be a much more complex genetic phenomenon than previously imagined.”
ACF researchers have not abandoned their breeding efforts, but a second way has been explored for several years: genetic modification.
Working on a transgenic version of the American chestnut, researchers at the State University of New York at Syracuse have developed a specimen that shows “very promising early results” of disease resistance, according to Vasiliy Lakoba, a collaborator with the researchers.
Combining the two methods can “produce better results,” he says.
“At least two centuries”
Once a resistant specimen is developed, it will be time for large-scale reimplantation. A task especially complicated by the upheaval of landscapes that became without the American chestnut during the last century.
“So much has changed in terms of climate, invasive species, pollution, habitat, land use, soil erosion,” explains Vasiliy Lakoba.
“It’s not the same world as it was 100 years ago.”
The researcher also says he expects “continued pressures” on American chestnut and other species in the future with climate change.
“In general, there will be more parasites, more diseases (…) which are probably already there, but which have not yet erupted…”, he underlines.
And the American chestnut’s renaissance won’t happen for years, or even decades, to come.
“It certainly represents a mission at least two centuries into the future,” says the researcher, who nevertheless says he is very optimistic about the success of their mission.
“It’s just a matter of time.”
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A canker on an American chestnut tree at the American Chestnut Foundation Research Farm, Oct. 4, 2022 in Meadowview, Va.
• Brendan Smialowski
Vasiliy Lakoba, director of research for the American Chestnut Foundation, compares a Chinese chestnut leaf (above) with that of an American chestnut, Oct. 4, 2022 in Meadowview, Va.
• Brendan Smialowski
Chestnut seedlings in a light room at the American Chestnut Foundation Research Farm, Oct. 4, 2022 in Meadowview, Va.
• Brendan Smialowski
Vasiliy Lakoba, director of research for the American Chestnut Foundation (ACF), in a grove of chestnut trees, Oct. 4, 2022 in Meadowview, Va.
• Brendan Smialowski
A young American chestnut seedling at the American Chestnut Foundation Research Farm, October 4, 2022 in Meadowview, Virginia
• Brendan Smialowski
Chestnut bug harvest at the American Chestnut Foundation Farm, October 4, 2022 in Meadowview, Virginia
• Brendan Smialowski
American chestnut seedlings at an American Chestnut Foundation nursery on October 4, 2022 in Meadowview, Va.
• Brendan Smialowski
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