“when the nuts were falling like manna from heaven,”

April 30, 2019 10:22 AM

The American Chestnut Tree: A GMO Story [YouTube] “"The American chestnut, once a dominant species in eastern North American forests, was decimated in the first half of the 20th century by a fungal blight (Cryphonectria parasitica, also referred to as chestnut blight) and logging. Researchers at the State University of New York College of Environmental Science and Forestry are developing a genetically engineered (GE) blight-resistant American chestnut (AC), and hope to win government approval for its unregulated release into the environment. If they are successful, the GE AC will be the first GE forest tree species planted specifically to spread freely through forests.” [via: NPR's On Point] [.PDF "Biotechnology For Forest Health? The Test Case Of The Genetically Engineered American Chestnut]

• Blight fight: the story of America’s chestnuts offers hope for British trees [The Guardian]

“Chestnut country once occupied some of the most spectacular wooded landscapes in the world, from the Shenandoah valley and the Catskills to Tennessee’s Smoky mountains. It is deep-gorge and clear-river country, where an understory of vibrant dogwood gives way to an imposing hemlock, a tulip tree or an exhilarating view. But something is amiss. When I visited last autumn, these woods would have been littered with fallen nuts from the magnificent American chestnut (Castanea dentata) – but for the blight that erased 4 billion trees from the landscape. Just under a century ago, the American chestnut disappeared from the vast eastern forests of the US. A broadleaf of immense size and distribution, the chestnut suffered catastrophic decimation by the inadvertent introduction of an Asian blight, Cryphonectria parasitica. The blight arrived in 1904, on ornamental Japanese chestnut trees imported to furnish New York’s expanding Bronx zoo. Infection swept north and south, and by the 1950s the great “redwood of the east” – whose fruit was relied upon by herbivores such as the wild turkey, bluejay and red squirrel – all but vanished, a tragedy considered one of the greatest ecological disasters to hit the world’s forests. Thankfully, however, the story did not end there: following a monumental conservational effort, the chestnut now stands on the brink of return.”

posted by Fizz (21 comments total)

If you are interested in trees at all (or even if you aren't), I highly recommend this year's Pulitzer Prize winner, The Overstory by Richard Powers. It's fantastic (and has made me love trees).
posted by aaronbleyaert at 10:59 AM on April 30, 2019 [21 favorites]

I appreciate how science can help us when it comes to something like this. That being said, I distrust this kind of science when a large corporation/government becomes involved because they're very likely to use this research in a predatory way that will only lead to further destruction/abuse. It's such a devil's bargain that I almost wonder if we're better off just leaving it alone. We had our chance with the AC and we fucked it up, so maybe we don't deserve to have these trees back.
posted by Fizz at 11:03 AM on April 30, 2019

This is amazing, thank you!

From the YouTube clip: This GMO product was accomplished by introducing a wheat gene coding into the genome for the American Chestnut Tree. [It could help other tree species: Diseases such as Dutch Elm Disease may be controllable through GMO technologies.]

Oh, man: Landscape architect Samuel B. Parsons, Jr. (wiki) is remembered primarily for his accidental introduction of the fungus that led to the near extinction of the formerly widespread American chestnut tree. Parsons was also a nurseryman, and in 1876 he imported Japanese chestnut trees for clients. His legacy is his inadvertent contribution to one of the greatest ecological catastrophes in American history, though he designed NYC's Morningside Park, St. Nicholas Park, and Union Square. Parsons also provided the original design for San Diego's City Park, which became Balboa Park.

Scientific American in 2014 on transgenic, blight-resistant chestnuts: One of the most frequent diners at chez chestnut was the now extinct passenger pigeon because of course it was. Not only did the trees provide hoards of nuts, they also offered massive and sturdy branches on which the birds could safely roost and breed. Enormous flocks were notorious for breaking weaker branches with their weight. All right, already! SA also notes: Chestnut leaves decay much more quickly than tougher, lignin-rich oak leaves, releasing plenty of nutrients for the aquatic larvae of various insects. Fallen American chestnut branches created animal habitats, the trees themselves likely altered soil in positive ways, not to mention the priceless contribution to air quality...

TIL that the chestnut tree next to my Queens elementary school was an Aesculus hippocastanum, a.k.a. horse-chestnut, and it's actually for the best we pelted one another with its poisonous conkers rather than crack them open.
posted by Iris Gambol at 11:25 AM on April 30, 2019 [4 favorites]

Chestnut trees are incredibly messy but they are magnificent trees and I would welcome their return devil's bargain or no.
Shade, chestnuts and easily compostable leaves - well worth the mess.
Just my $0.02
posted by speug at 11:30 AM on April 30, 2019 [3 favorites]

I'd be in favour of re-introducing native plants once we figure out how to neutralize whatever killed them off. Not just the American Chestnut but how about Elms or Ash trees?
posted by any portmanteau in a storm at 11:36 AM on April 30, 2019 [2 favorites]

Note to self: don't introduce non-native species when landscape gardening. It rarely goes well.

(I've been recently binge-watching Star Trek: Enterprise, and frequently find myself screaming at the screen: no, don't take the dog! You don't know what pathogens he has and/or will pick up from the alien environment! For that matter, you should be wearing your environmental suits, too! If I had been on the writing team, 2/3 of the plots would never have happened.)
posted by jb at 11:36 AM on April 30, 2019 [9 favorites]

There's a whole book on the life, death, and rebirth of the American Chestnut...
posted by PhineasGage at 11:50 AM on April 30, 2019 [3 favorites]

As long as Big Chestnut doesn't start suing farmers who just happen to live downhill and have the stray GMO'd chestnut roll onto their property and then take root, I'm fine with this.
posted by thecjm at 12:36 PM on April 30, 2019 [3 favorites]

There have been individuals and research groups working on breeding blight-resistant chestnuts for the past half-century or so. That's the problem with conventional plant breeding: it takes years to decades to discover if the gamble paid off. With contemporary plant breeding/gene splicing, it's much faster and cheaper to find and target the genes controlling the traits you're looking for. I've been following the work of Badgersett Farms in MInnesota for the past several years; they have several varieties showing various degrees of blight resistance, but resistance does not equal immunity, and the degree of resistance can be affected by location and climate. It's unlikely that there will ever be one variety to establish everywhere, even with the help of modern genetic engineering. Mother Nature is all about diversity.
posted by Lunaloon at 12:48 PM on April 30, 2019 [8 favorites]

I'd be in favour of re-introducing native plants once we figure out how to neutralize whatever killed them off. Not just the American Chestnut but how about Elms or Ash trees?

Plant pathologist here: hey, we're working on it! It's hard to deal with forest tree diseases: even if you have a treatment, it may be too expensive to be deployed. Elm trees at Penn State University and on the National Mall have been protected for years, but there's no way to stop the treatment: you have to keep injecting them; that's a good way to see resistance develop in the fungus. And it's certainly no solution on a large scale. Traditional breeding programs are slowly but surely coming up with resistant trees that look like American Elms.

As for ash, that's a difficult one- the beetle carrying the disease is so fast it's hard to stop it. However, there is research to find natural enemies of the beetle.

Researchers have done groundbreaking work trying to protect chestnuts: first a hypovirulent strain of the chestnut blight fungus was developed, which, when infecting a preexisting chestnut canker, will lessen the amount of disease that will develop. That will only happen with compatible strains of fungi, but recently a team of researchers came up with a universal donor strain of hypovirulent chestnut blight that is compatible with all the strains present in the US.

I'm a member of the American Chestnut Foundation, so I've watched over the last decade as it became clear to the Foundation that its breeding effort was not coming up with good enough results, and it's single-minded focus on blight left the chestnuts still susceptible to Phytophthora cinnamomi, a pathogen found in the SE US that will kill chestnuts in moister areas. Their citizen scientists have an almost religious devotion to natural breeding, and I'm not sure how they'll embrace these new trees. Those trees are part of the new generation of gene-editing technology, and so don't have all of the concerns of the old GMO technology.

If you'd like a nice piece of fiction about chestnuts, all my pathology friends and I loved Barbara Kingsolver's "Prodigal Summer". Kingsolver interviewed some of my friends for it!
posted by acrasis at 1:25 PM on April 30, 2019 [62 favorites]

Okay, but I'm not putting it in the baby food.
posted by theora55 at 1:37 PM on April 30, 2019

This is a good post, thanks.
posted by theora55 at 1:38 PM on April 30, 2019 [2 favorites]

Thanks, Fizz, and thank you, acrasis. Prodigal Summer is still one of my favorite books
posted by Maxwell's demon at 3:38 PM on April 30, 2019 [1 favorite]

Yessss, I can't wait for these trees to be available!
posted by Drosera at 4:18 PM on April 30, 2019 [1 favorite]

Yessss, I can't wait for these trees to be available edible!

Fixed.
posted by Fizz at 4:33 PM on April 30, 2019 [1 favorite]

SA also notes: Chestnut leaves decay much more quickly than tougher, lignin-rich oak leaves, releasing plenty of nutrients for the aquatic larvae of various insects. Fallen American chestnut branches created animal habitats, the trees themselves likely altered soil in positive ways, not to mention the priceless contribution to air quality...

Funguses are a big contributor to leaf decay, and I'd imagine a lack of fungus inhibitors allowed rapid nutrient recycling from the leaves, but also left the trees themselves open to fungal attack.
posted by jamjam at 5:56 PM on April 30, 2019 [3 favorites]

I love this thread and wish it could turn into an AMA for the SUNY crew.
posted by drowsy at 4:14 AM on May 1, 2019

Oh, that old chestnut.
posted by aspersioncast at 9:25 AM on May 1, 2019 [2 favorites]

There's chestnut stumps that have been kept alive by the rest of their forest for something like a hundred years. I wonder if the GMO process can be streamlined enough to take samples from those and then re-introduce the saplings? It would increase genetic diversity, plus there would be something poetic about it.
posted by tavella at 9:40 AM on May 1, 2019 [1 favorite]

There's chestnut stumps that have been kept alive by the rest of their forest for something like a hundred years

The canker doesn't take out trunks until they have reached 20 ft high or so, so old stumps can keep re-sprouting forever. There are actually thousands of chestnut trees lurking in forests this way. Originally, when the Foundation started its breeding program it used only a few parental types, then realized that it hadn't incorporated much of the genetic diversity that must exist from region to region in the large natural range of the chestnut. So in some of the last crosses, they had their local chapters use survivor trees in their region in the local breeding plots to try to come up with a more diverse set of trees. It would make sense to use a diverse stock of trees with gene editing as well. There are a lot of survivors up in Maine, but they might not be the best trees to plant down south.
posted by acrasis at 1:13 PM on May 1, 2019 [4 favorites]

Those trees are part of the new generation of gene-editing technology, and so don't have all of the concerns of the old GMO technology.

I'd love to learn more about this. From this article it sounds like the modified trees were made using Agrobacterium, a technique which has been around long enough that even I (who left lab work 17 years ago) am familiar with it. Is the reduced concern because the introduced oxalate oxidase enzyme is relatively benign? I feel like I am missing something.
posted by exogenous at 12:47 PM on May 6, 2019