Saving the American chestnut tree

The American chestnut tree was once a staple of U.S. landscapes, numbering over a billion. But by the 1950s, a fungus eliminated many of the species. Now, after 35 years of research, Professor William Powell has developed a blight-resistant American chestnut tree to restore the population.

TRANSCRIPT

The American Chestnut tree was once a staple of the U.S. landscape, numbering over a billion, but by the 1950's, a fungus had eliminated many of the species.

Now, after 35 years of research, Professor William Powell of the State University of New York College of Environmental Science and Forestry in Syracuse has developed a blight-resistant American Chestnut tree to restore the population, he hopes.

How did we get from hundreds of millions of trees to where we are today?

Well, what happened was that people started importing Asian Chestnuts about a century ago, and they did it for several reasons -- for orchards or yard trees or whatever.

But when they brought those over, they didn't realize that when you bring over a tree, you're not just bringing the tree over.

You're bringing all of the microbes that are on that tree.

And it turns out that there was one fungus on there that was a pathogen that the Asian trees could survive, but the American Chestnut was very susceptible to.

The fungus is happy -- it just finds a new population to feast on.

That's right, more food, and then it just spreads around.

So it came across and basically jumped off of the Asian Chestnut trees onto the American Chestnut trees.

It was actually first described at the Bronx Zoo in 1904, and from there spread throughout the range, as you said, killing billions of the largest trees in the forest, the American Chestnut.

And within 50 years, basically, they were functionally extinct.

Chestnut was such a common source, at least wood-wise.

Most of your decks on your homes were Chestnut.

It was very good for a woodworker to work with, right?

Actually, they used to say it would follow you from the cradle to the grave, because it was used to make cradles and graves.

In fact, as I was coming in today, I was at the railway station, and their benches there were all made out of American Chestnut.

So it was used for all kinds of purposes.

I'm thinking 'Chestnuts roasting over an open fire.'

It's so American, and the idea that the American Chestnut is where it's at... So, you've been in the lab mixing cultures of trees over time?

Yeah, so, I work very closely with the American Chestnut Foundation, and they first started what's called a backcross breeding program, where they would cross American Chestnuts with the Asian species.

So they mixed the two genomes, and then they backcross it to American to try to sort out all of the genes they don't want to have, but keep the resistance genes in.

About 6 years after that started, the New York chapter of the American Chestnut Foundation came to Dr. Maynard and myself at the College of Environmental Science and Forestry to see if we could take some of the newer approaches using genetic engineering to just put the genes in for resistance.

And that's how it got started.

About 27 years ago at ESF we started looking for genes, started developing methods to actually move genes into the tree.

That backcrossing that you were talking about, when you decided to cross these different genes, you want to figure out how not to carry on the negative traits?

Right.

So that's the reason why we started using genetic engineering in addition to traditional breeding, because in traditional breeding, what you do is you actually bring in all the traits and then you have to weed them out.

Some of the traits that you don't want to have -- the Asian Chestnuts are much shorter in height, typically growing only 40 to maybe 60 feet, and American Chestnuts would grow 80 to over 100 feet in height.

And that's important because American Chestnut was a canopy tree, and for it to reach a canopy in the eastern forest, it has to grow that tall.

So if you shorten it a little bit, it will no longer be a canopy tree.

Is there a way to bring this tree back?

I mean, what are the areas where we would start?

Okay, so, first of all, you have to develop a resistant tree, something that can survive the blight, and that's what we did.

So we now have a tree that we just added a single gene that confers blight resistance, and they get that out into the field.

One of the first steps we have to do is actually work with the federal government to get our regulatory approval.

We work with the USDA, EPA, and FDA for that.

After that, we're going to start a breeding program where we try to rescue the genetic diversity of the trees that are still surviving.

There are still a few million American Chestnut trees out there, and they're a diverse group.

So we can actually cross our trees that are blight-resistant with them and kind of get those genotypes back into a restoration population.

Are there specific areas?

Like when you look out in Appalachia, there are huge swaths of mountain tops that have been removed for coal mines that are basically shut down, but you're still left with a pretty big and barren landscape.

Would these kind of trees work?

Absolutely.

As a matter of fact, one on the things we don't want to do in the restoration program is cut down some really nice oaks and stuff like that to replace them with Chestnuts.

Instead we would rather look at places that are already devastated, that do not have the forest there anymore, and mine land reclamation is actually a great place to start.

These are places with mountaintop removal type things, but you want to turn it back to a natural ecosystem.

Those places we could actually put Chestnut back, not by itself, but along with other species that it normally would co-habitate with and kind of do a restoration on those lands and kind of let it spread from there.

So how long would it take to get it?

Obviously we have less land now that is pure forest than we did 50 years ago where these Chestnuts were, right?

But to try to bring the American Chestnut back to a place where it is vibrant, competitive, and blight-resistant.

So it's not going to be quick.

Chestnut is not a weed.

It does not spread quickly, probably only a couple miles per hundred years on its own.

So it's really going to depend on people planting them.

We really want to get people involved, not only our generation, but the next generation, and the following generation, because it's a century project to get it really back to where it was before the blight.

All right.

William Powell, thanks so much for joining us.

Thank you.