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"King of the eastern forest," an American chestnut in central Maryland in 1914. Photo: US Forestry Service
"King of the eastern forest," an American chestnut in central Maryland in 1914. Photo: US Forestry Service

Bio-engineering the return of the American chestnut

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The American chestnut tree was once known as the "king-of the eastern forest." It tree grew more than 100 feet tall and 6 feet across, and accounted for a quarter of the timber in the woods. Its straight-grained wood was remarkably resistant to rot, and its nuts were a reliable source of food.

The chestnut was wiped out by blight in the early 20th century, but now scientists in Syracuse think they're close to bringing it back. Our story comes from David Chanatry with the New York Reporting Project at Utica College.

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Reported by

David Chanatry
Reporter, New York Reporting Project at Utica College

84-year old Bill Coffin has spent a lifetime in love with the woods.

"What you’re looking at is shag bark hickory, pin oak, and cherry I would say. I don’t see any maple but it’s in there."

What Coffin knows is not in there is the American chestnut.  Sitting on the deck at his log home near Syracuse, he recalls playing childhood games, tossing horse chestnuts at his friends. But even back then he knew those weren’t the real thing.

"We were told by our parents that that was not the real chestnut, the American chestnut. They were very much aware of the disastrous blight. It was almost like the sinking of the Titanic, you know. . ."

The chestnut blight was first noticed in New York City in 1904, and within 50 years it killed as many as five billion trees from Maine to Georgia. The culprit was a fungus that piggybacked on an imported chestnut tree from Asia, says Dr. William Powell of the SUNY College of Environmental Science and Forestry.

"The trees from Asia had co-evolved with this fungus and had some resistance to it.  But it came to the United States, the trees here had never been exposed to this fungus, so the trees had no defense."

But if Powell and his colleague Dr. Charles Maynard are successful, the American chestnut might soon have a way to fight back. They’ve bio-engineered the tree to resist the blight.

Turns out the fungus does its dirty work by making something called oxalic acid. That acid produces a dead spot or canker which grows around the tree and stangles it. The scientists are taking advantage of gene found in wheat that detoxifies the deadly acid.

"What you’re doing is putting it into a single cell of a tree. You have to regenerate a whole tree from that single cell in order to have the gene in all the cells and to be able to pass it to the next generation."

In Powell’s lab, technicians like Linda McGuigan are growing forests of little chestnut trees in petri dishes.

"They were tested to see if the gene was actually incorporated into the genome and now my job is I’m going to grow them up, multiply them, and make them into little plants."

Those plants eventually—with a little help from bright lights in a growth chamber—get big enough to produce pollen. . . pollen with the new resistance-enhancing gene.

And here’s the gee whiz part—remember all those dead chestnut trees?—they’re just dead above ground. Microbes in the soil kill the fungus so millions of the root systems are still alive, sending up new shoots. They don’t get very big before the blight gets them, but some get big enough to produce flowers that can be pollinated with the transgenic- pollen. Some of the resulting trees will have the new gene.

"This is a chestnut we planted about four years ago."

At a SUNY field station in Syracuse, Andy Newhouse is looking for proof all this works. He’s working his way through several rows of tightly packed chestnut trees. Newhouse is measuring the cankers on trees they’ve intentionally infected with the blight.

"This particular tree, we just inoculated with the blight fungus this spring. And the resulting canker has grown—quick measurement here—to 47 millimeters long."

That’s half the size than on a tree without the wheat gene. It’s good, but not good enough. Now Powell and his team have added in a second gene, and preliminary tests show those trees to be the first American chestnut trees highly resistant to the blight. That, as they say, is a big deal.

If the results hold up in field tests, Powell will apply to the EPA, the Department of Agriculture and, because these produce nuts, the Food and Drug Administration for approval to distribute the trees.

"My hope is that five years from now we will be passing out trees to the general public for planting."

His colleague Dr. Maynard says from there, nature can take over.

"They’re no longer planted, only planted by the squirrels and blue jays and everything else. That’s when the true restoration is going to happen, when we see them popping up where we didn’t plant them."

It’s a century-long project, they say, to restore the "King."

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