The once-mighty American chestnut tree, which was virtually wiped out by a pathogenic fungus that arrived in New York City more than 100 years ago, returned April 18 to the area where the blight was first discovered in the Bronx.
Researchers from the SUNY College of Environmental Science and Forestry (ESF) in Syracuse, N.Y., with supporters from The American Chestnut Foundation, planted 10 transgenic American chestnut trees at a test site in The New York Botanical Garden. The scientists say there is reason to believe this field trial will reveal a variety of American chestnut that can survive a blight attack.
"We've been working on this for a long time and are looking at many genes. One particular gene has become my favorite," said Dr. William Powell, a plant biotechnology expert at ESF. "And over the years it has convinced me that this gene is going to do the trick."
Powell and his colleague, Dr. Charles Maynard, a tree improvement specialist, are enthusiastic about a gene derived from wheat that they have shown to increase resistance to a fungal pathogen in hybrid poplar. Powell and Maynard believe this gene will also be effective in the American chestnut because it detoxifies the oxalic acid produced by the blight pathogen. Oxalic acid kills the trees by attacking the cambium, the part of the tree that allows it to continue reproducing cells. A canker forms and everything above the canker dies. The roots can remain healthy and continue to send up shoots but the trees die back to ground level within a few years.
"If we can eliminate the oxalic acid, we probably will get a resistant tree," Powell said.
The American chestnut was once a dominant species in the forests of the eastern United States; it accounted for 25 percent of the trees in the forest. A healthy one can grow more than 100 feet tall and measure 10 feet in diameter.
"This was a key species in the eastern forest. It was super at producing nuts for wildlife; very important for agriculture for human consumption of the nuts; very important for the lumber industry, making a rot-resistant, fast-growing wood product; and it was an important part of our history," Powell said. "We really want to bring it back. The only way it can come back is to make a resistant tree because no one has been able to control the blight any other way."
The location of the planting is significant.
"We're very excited to be going back to The New York Botanical Garden because that's a stone's throw, literally across the street, from where the blight was discovered in 1904," Maynard said.
Author Eric W. Sanderson, in his 2009 book, "Mannahatta: A Natural History of New York City," wrote that when Henry Hudson first saw the island now called Manhattan in 1609, the American chestnut was "king of kings," making up more than half the trees in the forest.
Powell and Maynard, who describe themselves as the third generation of scientists searching for a solution, have conducted their research through the American Chestnut Research and Restoration Program at ESF, with support from the New York chapter of The American Chestnut Foundation, the Forest Health Initiative, ArborGen and many others. They were the first research team to run field trials of transgenic varieties.
The trees planted at the Botanical Garden are among more than 100 varieties of transgenic American chestnuts that are being tested in field trials or waiting to be tested for blight resistance. The planting is one of several events April 18 that celebrated the progress made during the 25 years that Maynard and Powell have devoted to the effort.
Before the planting on an open hilltop, the two scientists presented a lecture on the economic and ecological importance of the American chestnut tree, their research progress and the trees that were planted. After the trees were planted, the events concluded with an ESF Alumni reception and dinner in the Lillian and Amy Goldman Stone Mill on the Bronx River and adjacent to the native Forest in the heart of the Garden.
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