9:36am

Thu October 17, 2013
Environment

Scientists work to bring back American chestnut tree

The American chestnut tree was once known as the king of the eastern forest. It tree grew more than 100 feet tall and six 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.

Bill Coffin, 84, 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," Coffin said. "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," Coffin said. "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 here had never been exposed to this fungus, so the trees had no defense," Powell said.

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 strangles it. The scientists are taking advantage of a gene found in wheat that detoxifies the deadly acid.

"What you're doing is putting it into a single cell of a tree," Powell said. "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 are growing forests of little chestnut trees in petri dishes.
Those plants eventually—with a little help from bright lights in a growth chamber—get big enough to produce 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.

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," Newhouse said. "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.

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

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," Maynard said. "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.

David Chanatry is with the New York Reporting Project at Utica College.

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