Saving The American Chestnut

Chestnut trees are in danger due to an Exotic Fungus that entered this country over 100 years ago. With 4 billion trees being wiped out from this invasive fungus, Researchers are now using technology to keep this tree species alive.


Chestnut trees are in danger due to an exotic fungus that entered this country more than 100 years ago.

With four billion trees being wiped out from this invasive fungus, researchers are now using technology to keep this tree species alive.

Check it out.

I'm Bill Powell.

I'm Andy Newhouse.

Both: And we're here to save the American chestnut.

[ Laughs ]

Well, the American chestnut, first of all, you need to know, is one of the most common trees in the eastern forests.

In some places, it was one out of every four trees, and it was also one of the largest trees, and it was very important to wildlife.

We used to say that it fed everything from bees to bears and everything in between.

We lost the American chestnut because of an exotic pathogen that was introduced in this country a little over 100 years ago, and that pathogen is a fungus, came over on the Asian chestnut trees that people were importing at the time, and it jumped off the Asian chestnuts onto the American chestnut.

American chestnut had never been exposed to this fungus and was highly susceptible to this disease, chestnut blight, and within about 50 years, wiped out up to four billion of the largest trees in our forests.

Wow, and four billion was bow many of the total number of American chestnut trees?

So it basically infected all the American chestnuts within its range, and today it hasn't gone extinct yet, and that's only because the chestnut can survive at the roots.

Basically, it has the ability to resprout at the root collar, and it's interesting.

The fungus cannot kill the roots because the soil microorganisms protect the roots from the fungus itself.

And therefore, the tree resprouts.

It grows for awhile, gets infected, gets killed back down to the ground, so it's in a kind of a Sisyphus-like cycle.

Eventually, the roots will run out of energy, and the whole tree will die, but we still have millions of stump sprouts out there that we can use for restoration.

So, Andy, thanks for having us in to the lab here.

Tell us where we are and what goes on here.


We're in the greenhouse at SUNY ESF here in Syracuse, and the noise is ventilation system, keep the temperature stable both winter and summer, keep ideal growing conditions for our chestnut trees.

Many of these are actually second-generation trees already, so we've taken the pollen from the first trees we produced in the lab and crossed that with wild-type nontransgenic trees in some of our field plots, and then the offspring from those crosses, some of those inherit the trans gene, and those that do, we're growing up in here.

What are you trying to do, generally speaking, to try to combat this?

How do you fight the blight?

Okay, so we've taken kind of a unique path.

Actually, back in 1990, the American Chestnut Foundation New York chapter came to us asking, 'Is there another way to produce a blight-resistant tree other than crossing it with the Asian species?'

And we said, 'Well, there's this new technique called genetic engineering.'

And so we partnered with them and started this process of trying to find a gene, just a single gene, that would actually confer blight resistance to the tree, and we've actually found that.

The gene that we've used is from wheat, just like bread wheat that we eat, and so it's familiar.

People eat it already.

It's already in the environment.

It's present in a lot of native species also, but this one gene from wheat allows the American chestnut to tolerate infections by the blight fungus.

The way the fungus attacks a tree is that it makes an acid, and this acid actually kills the tree cells, and when it does that, it forms what's called a canker on the tree, and that canker eventually grows around the stem, girdling that stem, and choking off everything above.

So the idea here is there something that can stop that acid.

And I actually came across an abstract from a meeting where someone was putting a gene into another plant, a tomato, and this gene happened to encode an enzyme called oxalate oxidase, kind of a weird name.

But this enzyme, what it would actually do, is break down oxalic acid.

This is the acid the fungus uses to attack the tree.

So, hey, right here, eureka!

This is how we can stop the fungus from attacking the tree.

We take its weapon away by detoxifying that acid.


Why is the American chestnut important?

Why should we care about this one?

Who cares if it disappears?

Right, so it's important for many different reasons.

One is for the ecosystem.

It had a very consistent mass crop or nut crop, but it's not just the nuts.

It's also the leaves.

The leaves were used by insects, terrestrial as well as aquatic, which then fed fish and other organisms, but also there's benefits to humans, such as the wood itself is very valuable.

It's rot-resistant.

It's very straight-grained, easy to work.

People would use it for mainly outdoor purposes.

The nuts we could eat also.

'Chestnuts Roasting on an Open Fire,' you've probably heard that song around Christmastime.

And you could actually grind the nuts into a flour and use it for baking.

You can use it for brewing, to make beer.

So all different kinds of uses for the nuts themselves.

Basically, we're trying to figure out, 'How can we produce enough trees that once we have approval, we have a lot to give out to the public and start restoration programs?'

And that's why we partnered with the American Chestnut Foundation, which is a public organization.

It's a NGO.

And so we're going to be working with them to try to get people to plant mother trees so that we can outcross those.

We're going to actually be a big distributor of pollen for people in the beginning, and then they can plant those trees, keep outcrossing, and eventually increase more and more of the trees in the forest.

Should people be worried about the idea that you are messing with Mother Nature?

You know, Mother Nature didn't create the American chestnut with this gene.

Who are you to add it?

Well, I would say that we, as humans, have been messing with Mother Nature since we've domesticated plants.

And, really, this is kind of an extension of classical breeding.

And the wheat that we eat, and just about all the foods that we eat are not recognizable compared to their original nonmodified forms.

So this is another technology to do the same thing, to improve our foods or plants.

The chestnut blight was brought over here by humans.

It was our problem.

So I think we have the responsibility to fix that problem, and we've tried to do it for the past hundred years.

We couldn't until we had this new technology, biotechnology, that actually has allowed us to do that.

So we should use that tool to bring back this tree.