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FORCE, Pa.» Capping decades of research, two groups of plant breeders and geneticists appear to have arrived independently within reach of the same arboreal holy grail: creating an American chestnut tree that can, at long last, withstand the devastating fungus blight that wiped the trees out by the billions in the first half of the 20th century.
On 30 steeply sloped acres here in rural Pennsylvania, 1,000 potentially blight-resistant chestnut seedlings are sprouting with thousands of other hardwoods planted in May by the American Chestnut Foundation, a nonprofit group in Asheville, N.C., dedicated to the tree’s restoration.
The seedlings, Chinese-American hybrids, are among 14,000 chestnut trees being set atop reclaimed Appalachian strip mines through the end of 2014. The deployment, by far the largest to date, is seen as a crucial test of the tree’s ability to go it alone in wild forests full of predators and other species of trees competing for sunlight and nutrients.
At the same time, scientists at the State University of New York at Syracuse are readying new trials of an entirely different chestnut – not a hybrid, but one that has been modified with a gene from wheat that enables it to produce a blight-fighting enzyme.
That tree has also performed well in early tests. With approval of the federal Agriculture Department, researchers hope to begin a controlled field trial at a different reclaimed mine site as early as this autumn, in part to test the tree’s adaptability to harsh soils.
Placing genetically modified chestnut trees in the wild would require federal approval; for now, the altered chestnuts can be raised only in orchards and other places where there is no potential for their pollen to fertilize other trees.
"If in the field they look good, which we’ll find out about two years from now, those trees will be prime to be regulated," said William A. Powell, a professor and forest biotechnologist at the university’s College of Environmental Science and Forestry. That, he said, would mean that petitions could be filed to lift federal restrictions on where they could be planted.
Success by either group would be the first victory in a battle that has lasted decades to restore the chestnut to its status as an icon in U.S. forests, and U.S. culture.
The fast-growing chestnut was among the tallest trees in Eastern U.S. forests, trunks that could soar 50 feet before the first branches appeared. Chestnuts were celebrated for their beauty and prized by furniture makers, among others, for their hard, straight, rot-resistant wood.
In cities, "the tree connected people to the natural world at a time when the country was urbanizing," Susan Freinkel, the author of the 2007 book "American Chestnut: The Life, Death and Rebirth of a Perfect Tree," said. In the southern Appalachians, where it was ubiquitous, the chestnut’s many uses – from wood to tannins to nuts that sustained not just wildlife but also people and their livestock – made it a "great provisioner" in a place where life could be hard, Freinkel said.
Perhaps 4 billion of the majestic trees dominated woodlands in the Eastern United States in the early 1900s, when the blight first arrived in New York on a boat carrying Asian chestnut trees. Frantic efforts to find a disease-resistant hybrid began in the 1930s, but virtually all of the original U.S. trees were dead by 1950.
The American Chestnut Foundation has spent more than 30 years trying to blend the fungus resistance of Chinese chestnut trees with the grace and hardiness of the U.S. ones. Powell and a fellow Syracuse geneticist, Charles A. Maynard, have been working together since 1990 to find a biotechnological solution to the blight.
The two men are co-directors of the university’s American Chestnut Research and Restoration Center. The American Chestnut Foundation’s New York chapter is a major financial backer of their work.
Though both groups appear to be on the verge of breakthroughs, neither is willing to express more than cautious optimism for now. "The evidence to date is very promising, but as with anything, we always want to underpromise and overdeliver," Bryan Burhans, the Chestnut Foundation’s president, said. "This is a science-based program. There are unknowns out there, and we don’t have the answer to every question."
Sara Fern Fitzsimmons, a Pennsylvania State University researcher who is the foundation’s science coordinator in the region, said the first in the latest generation of hybrids was planted around 2009 and is nowhere near maturity.
"We’re only five years in the fields," Fitzsimmons said. "You can’t really say anything much in forestry until age 15."
Yet there are good reasons to believe that the main question now about a renaissance of chestnuts no longer is whether it will occur, but how soon. The foundation’s breeding program has created entire generational lines of trees that not only appear to fight off blight, but also have the hardiness and diversity needed to thrive anywhere in the chestnut’s traditional range of Louisiana to Maine.
The tree devised by Syracuse geneticists, meanwhile, must still be bred with other American chestnuts to guarantee that same diversity and hardiness. But the genetically modified chestnut starts with an advantage: unlike the hybrid – it was never crossed with a Chinese tree. When and if it is planted in the wild, researchers can be confident that it will grow like any other purely American chestnut.
The sixth and latest generation of hybrids has been bred to look and behave as much as possible like its U.S. forebears. But its genomes still hold thousands of Chinese genes that could, at least in theory, produce undesirable traits as the trees age.
That is important, because the trees need more than blight resistance to make it outside an arborist’s care. Even resistant trees will succumb to blight, for example, if they cannot adapt to environmental stresses like cold and drought. And even hardy trees will die out if they cannot hold their own against others in the battle for sunlight and nutrients.
"We have trees that we know are resistant. We have ones that are not," Fitzsimmons said. "It’s a matter of figuring out which one is which – throwing them out in the forest and saying: ‘OK, they can handle the blight. They can handle the competition. They’ve got American character, and we’re good to go.’ And that’s what we’re testing right now."
The two new American chestnuts take vastly different routes toward combating the blight, a parasitic fungus.
The fungus kills by producing oxalic acid, a potent chemical that even today is used as a wood bleach. The acid causes the tree to form a canker, which surrounds the tree trunk, and the chestnut quickly dies.
The new hybrid trees resist the fungus as their Chinese cousins do, essentially building a wall around the fungus before it can secrete enough acid to encircle the tree. American chestnuts had the ability to wall off diseased areas, but moved too slowly. With genes from their Chinese cousins, they can react more quickly.
The genetically modified chestnuts take a different approach: their wheat gene manufactures an enzyme that renders oxalic acid harmless, stopping the fungus before it can kill.
The two groups’ timing is no small wonder, said Maynard, the Syracuse geneticist. We’ve been in a footrace for 20 years," he said, "and it’s amazing that we’ve gotten to the same place at about the same time."
The more the merrier, said Burhans, the foundation president. "This is a war against chestnut blight," he said. "And we leave nothing off the table when we fight."
