Interesting short article about American Chestnut research at PSU

[Jim Becker]

https://www.psu.edu/news/research/st...0wHk8n94WwO09E

[Roger Feeley]

I’ve been watching the work on the American Chestnut for a long time, hoping to plant one someday. There are two efforts underway that I know of.

The American Chestnut Foundation crossed a surviving AC with an Asian chestnut. Picking the blight resistant ones, they started “back crossing” which is to cross the hybrid with AC to eventually breed a tree that is mostly AC but blight resistant. This has been going on for a long time and will still take many years.

Meanwhile, somebody edited the AC with CRISPR and inserted a single gene that makes AC blight resistant. Called Darling 58, this tree is pretty much ready to go. Drop mic, right? Not so fast. They need approval from USDA and there is controversy. The environmental crowd are opposing it and the major lumber producers are lobbying for it. It seems that approving this GMO chestnut would set a precedent and the lumber producers have a bunch of tree species on deck.

I think I have all this right. Feel free to correct me.

This is all frustrating for me. I live on a property in Virginia that could really use a couple of American chestnuts. I would be happy to plant a couple of Darling 58s.

[Brian Tymchak]

I'm beginning to think native American hardwoods are doomed. The EAB is about to finish off the last of the Ash trees, the Twig beetle is taking out the Walnuts, and the Asian Longhorn Beetle is going to take out the rest.

[Jim Becker]

Roger, a number of the things you mention are brought up in that short article. It appears that the only way to get beyond this is with the hybrid/genetic approach in some way helping to provide enough resistance to the blight so that the trees can naturally reproduce. But the thing it raises about risks to other species like oak that largely replaced the chestnut in the forests is eye opening. It's all interlocked...and I share Brian's concerns to at least some extent. (I lost every single ash tree on our old property over the past x years...and know that the black walnut is also at risk there)

[Ed Mitchell]

Shannon Rogers mentioned a slightly different twist on this on his lumber industry update podcast -- if we ignore the genetically engineered concerns for a moment, Shannon said we need to remember that the chestnut used to dominate many regions of the American forest. If we bring it back and give it immunity to whatever Asian wood-covid that killed it off in the first place, we should expect it to again dominate many forests.

So it's something to discuss. Do we want the oaks and cherries and etc which have since filled in to be out-competed by the chestnut, or are we better off with chestnut not being the top dog in the forest? Obviously I'm not talking about managed forests, I'm talking about forest preserves, national parks, etc, but IDK what impact there might be on silvacultural practices -- right now, silvaculturalists don't have to worry about some chestnut seeds being dropped by birds into their (eg) white oak grove and ruining the crop, but maybe that would change if the chestnut seeds were souped-up by CRISPR? Perhaps it will increase costs to grow (eg) white oak, etc, because extra time/effort will need to be expended to keep the super-chestnuts from out-competing whatever desired tree is supposed to be growing.

And certainly in the last century + the animals have adapted to the current environment. Perhaps some species have been selected out, certainly many species' places in the hierarchy have changed. Would an introduction of the super-chestnut cause a great stress on current animal populations as they are forced to re-adapt, and would we benefit from the end-result of that, or would we rather keep things they are? It can be hard to accurately forecast such things.

It's also a precedent for going forward. If we introduce a genetic change to protect chestnuts from this disease or bug, what happens when the next one comes along, as mentioned in the article? And the next and next and etc? And then other trees, like the walnut tree? Is there any risk to humans who eat walnuts or work with walnut wood from walnut trees with 4,216 different CRISPR changes to their DNA? What about animals? I doubt there's much science on such topics, so if we're going to become regular DNA-tinkerers, we might want to get serious about the science of risks around such activities.

[Jared Sankovich]

Shannon Rogers mentioned a slightly different twist on this on his lumber industry update podcast -- if we ignore the genetically engineered concerns for a moment, Shannon said we need to remember that the chestnut used to dominate many regions of the American forest. If we bring it back and give it immunity to whatever Asian wood-covid that killed it off in the first place, we should expect it to again dominate many forests.

So it's something to discuss. Do we want the oaks and cherries and etc which have since filled in to be out-competed by the chestnut, or are we better off with chestnut not being the top dog in the forest? Obviously I'm not talking about managed forests, I'm talking about forest preserves, national parks, etc, but IDK what impact there might be on silvacultural practices -- right now, silvaculturalists don't have to worry about some chestnut seeds being dropped by birds into their (eg) white oak grove and ruining the crop, but maybe that would change if the chestnut seeds were souped-up by CRISPR? Perhaps it will increase costs to grow (eg) white oak, etc, because extra time/effort will need to be expended to keep the super-chestnuts from out-competing whatever desired tree is supposed to be growing.

And certainly in the last century + the animals have adapted to the current environment. Perhaps some species have been selected out, certainly many species' places in the hierarchy have changed. Would an introduction of the super-chestnut cause a great stress on current animal populations as they are forced to re-adapt, and would we benefit from the end-result of that, or would we rather keep things they are? It can be hard to accurately forecast such things.

It's also a precedent for going forward. If we introduce a genetic change to protect chestnuts from this disease or bug, what happens when the next one comes along, as mentioned in the article? And the next and next and etc? And then other trees, like the walnut tree? Is there any risk to humans who eat walnuts or work with walnut wood from walnut trees with 4,216 different CRISPR changes to their DNA? What about animals? I doubt there's much science on such topics, so if we're going to become regular DNA-tinkerers, we might want to get serious about the science of risks around such activities.

For as much oak wilt as I saw last year I'll be surprised if there are any oaks left in a few years.

[Bernie Kopfer]

To Ed Mitchell: Thank you for your thoughtful comments and questions about this situation. Too often we humans have jumped in with no thought about potential long or short term consequences, but voices like yours might help minimize that in the future.

[Jason Lester]

The ACF research farm is near our house and farm. I'd personally love to see them back. So many homes, barns, and furniture in this area was built mainly from Chestnut. It's beautiful wood and so easy to work.

[roger wiegand]

The amount of adaptation that insects and animals can make to a changing food source in a few centuries is effectively zero. Doug Tallamy has done research showing that species introduced to the Americas nearly 600 years ago are typically used by less than 5-10 native insect species for food or reproduction, while a native oak is used by 600+. It takes on the order of 100,000 years for any significant adaptation to begin to happen.

The chestnuts have been gone from our forests for only 100 years or so, the tiniest blip of time; if reintroduced they would immediately return to a much-needed key role in supporting struggling native species. They were, for millennia, a keystone species in supporting north American forests and wildlife. It's very hard to imagine how allowing them to recover is a bad thing.

Strongly recommend Tallamy's books "Bringing Nature Home" and "The Nature of Oaks" if you are interested in the co-evolution of insects and their plant hosts. He's a U. of Deleware entomologist who does fascinating hard science research on this topic. Unlike most of us scientist types, his talks are wonderful-- spectacular slides of caterpillars!

[Patrick Kane]

I’ve been watching the work on the American Chestnut for a long time, hoping to plant one someday. There are two efforts underway that I know of.

The American Chestnut Foundation crossed a surviving AC with an Asian chestnut. Picking the blight resistant ones, they started “back crossing” which is to cross the hybrid with AC to eventually breed a tree that is mostly AC but blight resistant. This has been going on for a long time and will still take many years.

Meanwhile, somebody edited the AC with CRISPR and inserted a single gene that makes AC blight resistant. Called Darling 58, this tree is pretty much ready to go. Drop mic, right? Not so fast. They need approval from USDA and there is controversy. The environmental crowd are opposing it and the major lumber producers are lobbying for it. It seems that approving this GMO chestnut would set a precedent and the lumber producers have a bunch of tree species on deck.

I think I have all this right. Feel free to correct me.

This is all frustrating for me. I live on a property in Virginia that could really use a couple of American chestnuts. I would be happy to plant a couple of Darling 58s.

When can someone use CRISPR to create an intensely figure walnut variety that hits maturity in a decade?

Kidding aside, i think unleashing genetically modified plants unto the wild writ large is somewhat terrifying. Its kind of like stocking trout over native/wild populations. In the case of Chestnuts, i dont know of a single standing Chestnut tree within a day's drive of me. And I attended PSU, where they are a little nutty about trees. Those are some of the only American Elms of any stature that ive seen in my life. The Pattee Mall has multiple trees that date back to the late 1800s.

From a timber perspective, the chestnut tree grows quite quickly, right?

[roger wiegand]

If you want to be terrified consider that almost all of the plants you see when driving around inhabited areas and much of what you see in the forest and grasslands of America are non-native species that have been introduced by humans over the last 500 years. None of the turf grass, almost none of the flowering shrubs and trees and a only a tiny fraction of perennials and almost none of the annuals in gardens are native to north America. Adding back a single gene in a native species pales in comparison.

[Ed Mitchell]

The amount of adaptation that insects and animals can make to a changing food source in a few centuries is effectively zero. Doug Tallamy has done research showing that species introduced to the Americas nearly 600 years ago are typically used by less than 5-10 native insect species for food or reproduction, while a native oak is used by 600+. It takes on the order of 100,000 years for any significant adaptation to begin to happen.

The chestnuts have been gone from our forests for only 100 years or so, the tiniest blip of time; if reintroduced they would immediately return to a much-needed key role in supporting struggling native species. They were, for millennia, a keystone species in supporting north American forests and wildlife. It's very hard to imagine how allowing them to recover is a bad thing.

I've read Bringing Nature Home, (and I agree it's wonderful) and I think might you might be conflating "evolution" with "adaptation", at least as I remember Tallamy. Turning your car left to the grocery store because turning right leads to a street now under construction with heavy traffic -- that's an adaptation, and it takes no time at all. Evolution is how natural selection gets us from (eg) amphibians to humans, and yes, the tiniest increment of evolutionary time is hundreds of thousands of years.

A species which was dependent on the chestnut would have had no time to evolve, because our chestnuts vanished too quickly. They would have gone extinct (assuming they were truly dependent on the chestnut). Therefore, re-introducing the chestnut cannot help them, because they no longer exist. But a species which enjoyed the evolutionary advantage of having the choice to prefer the chestnut but is also able to survive with (eg) an oak -- that species could have potentially adapted once the chestnuts started to disappear.

You assume that allowing those species to recover is a good thing (and of course you might be totally right, we can't know for sure), but given that some species went extinct, and virtually all others now occupy different niches due to adaptation -- those species that might recover with the new super-chestnuts will not be entering the same world we had back in 1824 -- the extinction of some species and re-balancing of the rest will mean a new range of adaptations will have to occur, and we cannot pretend to know how that will shake out, as there are far too many variables. Some won't have predators which may have been plentiful back in 1824 and kept them in check, and now, without those predators they will run wild and cause unforeseeable damage in the modern world.

It's important to note that adaptation is a spectrum, not a point. Humans have adapted to live in extreme climates (think Eskimos) -- but they aren't exactly dominating the world, they're a small niche of (wonderful, hopefully happy) people. Now imagine that as it pertains to the chestnut. You've got 1000 species that interact with the chestnut in various ways. The chestnut disappears. Some will go extinct, and all the rest will adapt, but their adaptations, while allowing them to survive, do not necessarily mean they will prosper. Some will barely scrape by, like Eskimos, and some will really flourish. The stress of having to adapt will also expose those species to the vagaries of chance -- a forest fire, some years of hard winters or brutal summers or whatever -- can tip the scales.

I'm not saying one way is right or wrong. I'm just hoping we'll look before we leap, which is apparently not a strong suit of our species.

[Curt Harms]

I'm not saying one way is right or wrong. I'm just hoping we'll look before we leap, which is apparently not a strong suit of our species.

I think we're getting better, I just hope we don't go too far in the other direction.