Science AMA Series: We are a team of ESF scientists who developed a way to make American chestnut trees resistant to the blight that virtually wiped out the species 100 years ago. We’ll talk about how we can help restore this iconic tree to our forests. AUA!

Abstract

Hi Reddit! We are a team of scientists at the College of Environmental Science and Forestry in Syracuse, New York, and we’ve been working for 27 years to create an American chestnut tree suitable for restoration of our forests. Billions of these trees were killed by an invasive blight fungus that was first identified at the Bronx Zoo early in the 20th century. There are references to American chestnuts throughout our culture, with chestnuts roasting over open fires in the winter and Chestnut Streets running through towns across the country. Furniture made from American chestnut is long-lasting, as are barns that dot the countryside, because the wood is durable and rot-resistant. If the wood were available now, we might be building our backyard decks with it. Perhaps most significantly, the species’ abundant nuts were once a dietary staple for wildlife.

Our research team found a way to add one gene from wheat to the American chestnut’s 38,000 genes, to make it capable of withstanding what was once a fatal blight. It works by detoxifying oxalate, the major weapon the fungus uses to attack the tree. We use tissue culture to grow the trees initially, but we have now established seed orchards for future production. We continue testing to ensure these transgenic trees are safe for humans and the environment. The next steps are to establish a restoration forest for demonstration and research, and to obtain federal approval to distribute the trees to the public and introduce the trees into the wild.

Here’s an introduction to the people you’ll be speaking to today. We all represent ESF’s American Chestnut Research and Restoration Project.

• Dr. Bill Powell, director of the American Chestnut Research and Restoration Project

• Tyler Desmarais, master’s candidate in plant science and biotechnology

• Vern Coffey, master’s candidate in plant science and biotechnology

• Alex Levine, technician with the chestnut project

• Andy Newhouse, Ph.D. candidate in plant science and biotechnology

• Linda McGuigan, technician with the chestnut project

• Dr. Allison Oakes, postdoctoral fellow on the chestnut project

We’ll be back to start answering questions at 3 pm EST. We’re looking forward to it!

For more information on our project in general, see our page here: http://www.esf.edu/chestnut/

If you'd like to support or share our fundraising effort, our Fundly page is here: https://fundly.com/chestnutchallenge/

Joining the American Chestnut Foundation is a great way to show your support for chestnuts in general, and to keep up with both the backcross breeding program and our biotechnology work: https://www.acf.org/store/membership/

We're on Facebook (https://www.facebook.com/groups/esfchestnut/?ref=bookmarks) and Instagram (american_chestnut_project)

(And here's a recent issue of the Chestnut Foundation's journal, including a couple of articles on different aspects of our work: https://www.acf.org/wp-content/uploads/2017/03/Fall-2016-Chestnut-REV-1.pdf )

Edit: Because so many people asked about when the trees will come available, I will try to answer here. First, our trees have to go through a rigorous review by three federal regulatory agencies, EPA, USDA, and FDA. We have been communicating with them for the past two years to learn what data they need and and the process to submit. We believe we will be able to submit sometime this year (2017). From what we learned, we estimate the process will take between 2 to 4 years. While we go through the process, we are setting up nut production orchards as part of the 10,000 chestnut challenge so that we should have seedlings available as soon as we receive registration from the EPA, non-regulated status from the USDA, and an OK from the FDA. We will be working with The American Chestnut Foundation (www.acf.org) to help with the distribution.

When will you have seeds available for wholesale purchase? What are the masting yields from the trees you have brought to maturity so far?

billygoon9378

Check the comment we added to the introductory post at the top regarding distribution of resistant seedlings. So far, our resistant trees are producing pollen from male flowers, but they are not mature enough to make nut-producing female flowers. We are using the pollen to to make controlled crosses by hand pollinating the female flowers on non-resistant trees. We're also planting nut production orchards of resistant and non-resistant trees side by side for open pollination, but these trees still have a few years to grow before they will produce nuts.


Do you envision the chestnut could ever become a dominant component of forests in the eastern United States again, or do you think conditions now are too different from how they once were for the tree to reestablish? Also, what is your opinion about the hypothesis that native Americans did a lot of work to manage the land in the eastern United States to encourage 'staple crop' trees like chestnut and oak?

Aloiciousss

Aloiciousss, this is Linda McGuigan. It's going to be a long time, perhaps a century or more, before American chestnuts can dominant the Eastern forests of the United States again. We need help from the public to plant Mother Trees that can be breed with our blight resistant American chestnuts. Members of the New York Chapter of The American Chestnut Foundation can contact Allen Nichols (fajknichols.75@gmail.com) for Mother Tree nuts. These trees won't have the blight resistance gene but once breed with our trees, half of the offspring will carry the resistance gene.

Indigenous People contributed to the spread of American chestnuts when they did low intensity prescribed burns. Chestnuts, along with oaks and hickories, are fire tolerant.


How much do you know about the natural variation of pre-blight chestnuts in the wild?

I'm wondering if gene editing can also later help to add back some of that diversity to the population.

mem_somerville

There has been some studies. The American chestnut was one of the last canopy trees to migrate back north after the last ice age because it spreads slowly on its own (estimate only a few kilometers per century). Therefore the southern part of the range has more genetic diversity than the northern. We at ESF and our partners at TACF have taken this in consideration as we plan out how to rescue the serving genetic diversity and incorporate it into a restoration population.


What do we know about the insects that relied on am. Chestnut as a host plant? Are they persisting on other castanea sp.?

Also when can I plant one of my own?

Esf alum here! Best school ever :)

zabulon_

Our colleague Giuseppe Tumminello published an article in 2016 on insects found on American chestnut trees - here's an excerpt:

"Specimens of more than 25 genera were collected from the five most speciose insect orders: Coleoptera (Beetles), Diptera (Flies), Hemiptera (True Bugs), Hymenoptera (Ants, Bees and Wasps), and Lepidoptera (Butterflies and Moths). Diptera and Hymenoptera showed the greatest diversity of floral visitors. This was not much of a surprise given that bees and groups of flies, notably Syrphidae (Hover Flies), are well-known pollen foragers. Another group of interest that showed prominent abundance was Cerambycidae (Long-Horned Beetles)"

An older article cites 5-7 species that fed only on chestnut - these are likely extinct. The only other american Castanea species, the American chinquapin (Castanea pumila, which has several subspecies that may be lumped in or claimed as different species depending on the authority) is also susceptible to the blight.

Reference: Opler, P. A. (1978). Insects of American chestnut: possible importance and conservation concern. In The American chestnut symposium (pp. 83–85). West Virginia University Press Morgantown, West Virginia.

Tumminello, Giuseppe. (2016). Insect Residents. THE JOURNAL OF THE AMERICAN CHESTNUT FOUNDATION, 30(2), 25–27.

  • V. Coffey

Thank you for doing this AMA. I have a question that might come off as trying to undermine the legitimacy of your project but I assure you it is out of curiosity not malicious intent.

Why is the European chestnut tree not suitable for reforestation? It seems to tolerate the blight and from what I can tell should grow in the US just fine. Why would it not be an acceptable substitute?

ponylover666

Good question. The European is also a nice tree, but unfortunately it is also susceptible to the blight and being a different species, isn't expected to be fully adapted to our forests. In Europe the blight is controlled using hypovirulence (a virus that reduces virulence of the pathogen), but to date hypovirulence has not worked in the U.S. We need a fully blight resistant trees that are adapted to our forests. That is why we took the approach of making a very small genetic addition to enhance blight resistance while maintaining 100% of the American chestnut genome.


Hello! Thank you all for taking the time to speak to us today.

I have a question regarding the durability of the wheat gene. Here I'm assuming it's a major resistance gene, and we've seen time and time again in wheat breeding that single major resistance genes can be easily overcome by the pathogen gaining virulence to previously resistant varieties through mutation. Do you have plans to introduce further resistance genes to reduce the time it takes for the pathogen to overcome host defenses, like how they pyramid resistance genes in agricultural crops?

Tsingya

(This is Andy) Good question, and certainly an important consideration in breeding for disease resistance! One very unique aspect of the oxalate oxidase (OxO) gene in chestnut is that it does not actually kill the blight fungus. Rather, it detoxifies a toxin (oxalic acid, or oxalate) that the fungus uses to damage American chestnuts. The fact that it doesn't kill the fungus means that this gene does not create a strong selective pressure against the fungus, so there is very little pressure for it to evolve resistance to the OxO. Basically, when the fungus grows on our transgenic American chestnuts, it behaves very much like it does on Chinese chestnuts or oaks - it might cause a small amount of damage, but mostly it persists "quietly" until the tree (or a branch) does from some other reason, then the fungus eats the dead tissue. In other words, the blight fungus acts like a saprophyte on Chinese chestnuts or our transgenic chestnuts, while it acts like a strong pathogen on non-transgenic American chestnuts. Additionally, as you suggest re. pyramiding, we're working with the Chestnut Foundation to think about breeding our transgenic American chestnuts with some of their backcross trees ( https://www.acf.org/our-work/backcross-breeding/ ), which should provide multiple mechanisms of resistance to blight, further reducing the chances of the fungus overcoming the tree's resistance.

For further information on OxO stability, see page 32 of the Chestnut Foundation's Fall 2016 Journal: https://www.acf.org/wp-content/uploads/2017/03/Fall-2016-Chestnut-REV-1.pdf (actually page 34 of the PDF, printed page number is 32, title is OxO Blight Resistance Sustainability)


Thanks for your work. Last time I read about this there was only a cross-breeding program (with the Chinese chestnut) that had decades to go. How long do you guess it'll be before we'll see mature chestnut trees in American forests?

suddenly_satire

Good points from CleverCards and cerdz, both are correct. The American Chestnut Foundation's backcross breeding program has had some success producing good blight-resistant trees, but they also have some work yet to do to optimize the process for more consistent blight resistance in whole seed lots. As for mature chestnut trees? They take a long time to grow! The very first blight-resistant trees that get planted, like those in our upcoming Restoration Forest, will be considered "mature" (flowering, at least) in a decade or so. But if we can start distributing the first blight resistant trees in a few years, it will be decades (at least) before many people see meaningful numbers of good-sized trees. We're calling this a century project - really hoping our grandkids can see big groves of healthy American chestnuts! It requires patience, but we need to start somewhere.


Are there any special considerations when growing plants in tissue culture compared to animal cells? How do you identify/choose where to insert the gene in the genome, and how do you ensure no other genes have been knocked out in the process?

RhyDonCorleone

Hi RhyDonCorleone, Chestnut Team member Alex here.

There are many differences between growing animal vs plant cells in culture, but what I can tell you is that Chestnut is comparatively difficult to grow in culture as compared to other trees such as poplar and elm. Another one of the challenges is that trees coming out of tissue culture grow slower than those that germinated from nuts. This is why our approach is to have transgenic nuts available as opposed to trees directly from culture. Currently, we are using Agrobacterium to transfect our chestnut lines. This process will randomly insert the gene into the genome. Due to this, we typically make several transformation "events", and then test them to see which have the highest expression of our inserted gene. For those individual trees with good expression, we then sequence their genome surrounding the inserted gene to ensure that there has not been disruption to other important genes. We are currently interested in CRISPR techniques to overcome this lack of control. Cheers.


Fellow Upstate NYer here.

If you are able to successfully repopulate American chestnuts in their original habitats, how do you think the ecosystems in American forests will change? Greater density of wildlife per square mile? More turkeys?

Regardless, you guys are doing a huge service to us by bringing back one of our nation's most important trees.

kuhllax24

Vern Coffey here. It is very likely that there would be a higher density of wildlife. American chestnuts produce a steady supply of food each year, unlike the other trees that are major sources of edible seeds (oak, beech, hickory); these trees have a cycle of "mast years", a year of heavy production followed by 1 or more years of very little production. Wildlife including Black bear, wild turkey, raccoon, squirrel, grouse, and many other birds and mammals, including predators such as the Cooper's hawk, peregrine falcon, bobcat, and cougar declined along with the decline of Chestnut, though habitat loss was also a large contributor. The passenger pigeon ate chestnuts, though we probably won't see their return unless the scientists working on de-extinction succeed. -

References:

Davis, Donald E. "Historical significance of American chestnut to Appalachian culture and ecology." In, Proc. of conf. on restoration of American chestnut to forest lands, Steiner, K.C. and J.E. Carlson, (eds.) (2006). http://ecosystems.psu.edu/research/chestnut/information/conference-2004/conference/davis

Hill, J. M. "Wildlife value of Castanea dentata past and present, the historical decline of the chestnut and its future use in restoration of natural areas." Proceedings of the International Chestnut Conference: 1994; Morgantown, West. Virginia. 1994.


I first learned about this in the Shenandoah national forest 20 years ago and I'm so happy to hear there is an answer! When and where will your trees start being seen in parks like the Shenandoah?

MutantMartian

Initially I envision our trees being planted on private lands, reclamation sites (like mine reclamation), botanical gardens and arboretums, and historical sites. As people learn more about the American chestnut trees and and see how they can benefit the environment, then we may see these trees planted in parks. This is why we are starting the long-term restoration forest research project ( https://fundly.com/chestnutchallenge/ ) that will study its environmental impacts compared to traditionally bred trees and the project will include a significant public outreach component.


Hey neat, my old professors are on reddit! I don't really have any questions about the project, because I asked them in class... BUT I think it's really great and I still, 6 or so years later, tell people about it!

Itsascrnnam

Thanks!. Keep spreading the work about the return of the American chestnut.


Could you talk about the risk assessment process and how you plan to manage any unpredicted events?

djnrrd

First, because we are making such a small change to the genome compared to hybrid breeding, the risk is much lower than for most chestnut trees planted today. Also we purposely choose a very benign but effective gene, oxalate oxidase (OxO), that comes from wheat. OxO is also found in many crop and wild plants and therefor is eaten by humans, livestock, and wildlife all the time (you probably ate some OxO today).

But, because we use the tools of genetic engineering, we are highly regulated by the EPA, USDA, and FDA. Here is a partial list of tests we are doing: nutrient content of the nuts, checking the inserted gene to be sure it is not a know allergen, toxin, or gluten protein, checking the gene insertion site to ensure we don't disrupt another gene, check nearest gene to be sure the insert didn't change expression, performing terrestrial and aquatic insect and amphibian feeding feeding studies on the leaves and leaf litter, mycorrhizal colonization of the roots, bumble bee feeding on the pollen, growth and form of the trees, native seed germination in leaf litter, and any possible allopathic effect on surrounding vegetation. We are not seeing any significant differences between the GE American chestnut and the wild-type or chestnuts produced by hybrid breeding. The data from these studies, as well as data from the literature about other plants, will allow us to apply for regulatory review.

But we are not done there. We have a stewardship plan for after we receive regulatory approval. This is why we are setting up the long-term restoration research forests to follow these trees and conventionally produced tree for decades (see https://fundly.com/chestnutchallenge/ ). We will report any unpredicted events. Unpredicted events may be positive, neutral, or negative and we will manage accordingly. All the evidence so far points to a positive outcome.


Do you think with this kind of information, you'll be able to start working on other trees who may be suffering, such as banana trees?

CarBowie

(This is Andy) Yes! In fact, other researchers are already working on this. Here's a recent update from Africa: http://allianceforscience.cornell.edu/blog/gm-bxw-resistant-bananas-start-their-journey-farmer The specific gene we're using (Oxalate oxidase from wheat) might not help the banana specifically, but it will likely benefit other plants that are threatened by fungal diseases.

More generally, our work, both specific lab processes and things like strategies for going through the regulatory process, should provide a "road map" for researchers working on other trees in the future. Currently, there is a very well-established pattern of large corporations developing agricultural crops and taking them through the regulatory process, but it is very rare for universities. This will also be the first time a wild forest-type tree has been submitted for regulatory approval, so some of the considerations and necessary experiments will be different than those needed for agricultural crops. We certainly hope our work with chestnuts will make things easier for other tree research groups!


If a private consumer wanted a 10 tree grove of your trees on their property (5 males and 5 females), what is the expected price?

Insis18

This is a common question, so please see edit on original post. Short answer, we are not at that point yet.


IIRC American Chestnut produces some amount of oxalate oxidase naturally?

Although a single gene has been introduced to increase production of this damage-limiting enzyme I'm curious how much more oxalate oxidase is produced by the transgenic samples and were multiple copies of the gene inserted to achieve this protective concentration or was the location of insertion (for instance in relation to promotor genes) a greater factor in enzyme production?

~ Proud ESF Alum

CleverCards

Hi CleverCards, Alex here.

American Chestnut does not have a native oxalate oxidase gene. It does have a ~79% homolog, but exhibits no oxalate oxidase activity in our tests. By comparison, our transgenic chestnut with the oxalate oxidase gene can have very high levels of expression depending on the transgenic line. We include a promoter with the transgene, and we are currently exploring difference promoters to tightly control oxalate oxidase expression. Thanks for the question.


Kind of an odd question... but I grew up having an american chestnut tree in our yard. Due to their scarcity we always felt obligated to keep it but from our perspective, as humans, it was just about the worst tree we could imagine: The fruits are huge, sharp, slick (sounds silly but they're a legitimate trip hazard), and ridiculously plentiful. They also destroy mowers so absolutely had to be dealt with every single week.

Obviously none of these are very big "cons" in the middle of a forest, and for wildlife I suspect they'd be absolutely fantastic. But it leads me to suspect as a society we're largely going to want lots of these in our forests and practically none of them in our yards.

So my question is simply, would that kind of zoning/isolation cause any problems?

tehm

There are plenty of trees that are found in forests but not planted in cities or yards for all kinds of reasons - maybe they have litter that is a nuisance (like your complaint with the chestnut), maybe they don't survive well in the urban environment, or other reasons. I don't think that causes any problems. It's worth noting that many people might want to plant american chestnuts in their yard or back woods, because the nuts are delicious! - V. Coffey


Hi guys. I originally identified the Mother Tree in Chestnut flats GA. How much of the DNA from found specimens is going into these individuals.

captdet

(Vern here) Our resistant trees are grown from a transformed embryo (that came from a tree here in New York), and are then propagated clonally. In order to capture the genetic diversity of the surviving species, we plan to cross the resistant trees with surviving wild trees. From these crosses, half of these offspring will inherit the resistance gene, along with half of the genes from the wild tree. The resistant offspring can be identified, and crossed again with other wild trees when they mature. We'll work with the American Chestnut Foundation and other groups to cross breed the resistant trees with regionally adapted trees throughout the range, such as trees in GA.


Hey! I'm workng on a planting of a few hundred blight-resistant chestnuts with The Nature Conservancy in Ohio. We're actually getting started tomorrow.

At what point will blight resistant chestnut seedlings become available to homeowners and just anybody who wants to buy them?

stoicsmile

See updates to OP re. timing, thanks!


How long until the first harvest? Will there be seeds for sale at any point?

3z3ki3l

Please see edit in original post. Thanks.


I recently bought a house and am planning what types of trees to plant into the almost tree-less yard. I am interested in planting some of these Chestnut Trees, and if anything it will help in your ultimate goal. Can you tell me if/when I would be able to purchase some seeds/cuttings?

andy83991

In a few years you will (see edit to original post). If you join TACF (www.acf.org), you can keep up with our progress and know when the trees adapted for your local area will become available.


Forgive the ignorance, but if the tree population was devastated why is the blight still around to affect it? Why is this not a situation where we can wait until the disease has run its course and then rebuild after?

Also i see you've been getting this a lot, but Syracuse alum here. Love the work yall at esf do!

FogItNozzel

pr06lefs is right, the blight fungus (Cryphonectria parasitica) survives on oaks, red maples, staghorn sumacs, and shagbark hickories. These species have some natural defenses, so they are not killed by the fungus, but this is why the fungus is now a permanent resident of our forests. -V. Coffey


Hi! Undergrad biology student here in central New York, interested in doing my graduate at ESF. I'm interested in knowing more about the process that got you here, whether you ever expected to spend this long on chestnut trees, and what kind of lab setup you're running to see how viable these trees are. Go plants!

ohboy_jpg

Hi ohboy_jpg, Alex here.

We've added a bunch of links at the top where you can find this information. Thanks for the support!


ESF grad here!! Oakies unite! I got the chance to do some research in the EFB dept during my time there so im excited to see this pop up on reddit. My question is, what was the most technically challenging aspect of this project?

NotRossFromFriends

(This is Vern) The answer to that probably depends on who you ask! It took over a decade (closer to two) just to figure out how to get chestnuts into tissue culture, grown into whole plants, and then acclimatized so they survive planting into the greenhouse and the field; this is a prerequisite to genetic transformation. Now that we have a procedure for tissue culture and transformation (which we continue to optimize), and trees that show very good resistance to blight, working with the federal regulatory agencies is currently our biggest challenge!


Will you continue to create new genetically altered chestnuts, or is there already enough altered stock for sufficient genetic diversity? What's the anticipated timeline for chestnut repopulation?

pr06lefs

(Vern here) The transformed trees have very little diversity. The plan is to recapture that diversity by crossing the resistant trees with surviving wild trees; half of the offspring will inherit the resistance gene, along with half of the genes from the wild tree. The resistant offspring can be identified with a quick test, then grown to maturity and crossed again with new wild trees. With this process, we can keep local adaptations by planting nuts from wild Georgia trees in Georgia, nuts from New york in New York, etc.


Is the end product (the chestnut) altered in any way that will affect wildlife/ propogation?

Like the ability for it to germinate and grow naturally, and the claoric content etc for it being eaten?

Also!

Do the trees look the same? Original vs adapted? And will that wood be as durable for building purposes?

8Bells

Thanks, 8Bells, for the great questions. Our blight resistant American chestnut trees have the oxalate oxidase gene inserted into them. This gene can be found in wheat, rice, corn, peanut, strawberry, and banana, to name a few. It's eaten every day. We have studied the impact our chestnuts have on leaf litter decomposition, native seed germination in the leaf litter, insect feeding on the chestnuts, as well as bees feeding on pollen. We have found no differences compared to traditionally breed America chestnut. We've done caloric nutritional tests and they are equivalent to traditional American chestnut. Also, because the genome contains all of the original genes, the trees look no different than traditionally breed American chestnuts and the durability of the wood should be the same.


Have you ever considered a project to try and recreate the primordial forests of the UK and Europe?

Bravehat

Interesting concept. We are focusing on rescuing the American chestnut right now.


How does this approach differ or compare to the Dunstan chestnut that was cross bred to eliminate blight?

Ithastobereal

The Dunstan is a hybrid of American and Chinese chestnuts; Chinese chestnuts have natural resistance to the blight. The Dunstan was produced by repeated crosses with 3 different lines of Chinese chestnuts and American chestnuts, and it is unknown what percentage is American. Our blight-resistant chestnuts retain 100% of the American genome, with the addition of a single gene from wheat.


How can I help?

Or more accurately, how can I get my hands on these trees to plant some!!!

StikyBoots

Hi StikyBoots. I'm Linda McGuigan, a technician on the American Chestnut Project. Thank you for wanting to help. The best way is by becoming a member of The New York Chapter of The American Chestnut Foundation (https://www.acf.org/store/membership/). As for receiving one of our blight resistant trees, there will be information at the top of the page shortly.


Thank you for doing this important work!

What gene did you add, what organism did it come from, how was it modified, what technique was used to insert it, and how did you decide the genome location for insertion?

RedCheekedSalamander

Hi RedCheekedSalamander! Alex here. The gene was oxalate oxidase, whose code was sourced from wheat. This wheat gene is also found in strawberries, bananas, and common grasses. It was not modified at all as compared to the wheat genome. We use an Agrobacterium transformation protocol to transfect the plants. This technique inserts the gene randomly in the genome, which is why we spend a lot of time characterizing exactly where it went via genome sequencing in order to ensure no essential genes were disturbed. Thanks for the question.


Can you say which climate zones in the US these will be suitable for? Can I have some in my Texas yard?

intronert

(This is Andy) I suppose it depends what part of Texas, but generally American chestnuts are best adapted to temperate climates with more moisture and cool or cold winters. Here's a range map where they grew naturally: https://www.acf.org/the-american-chestnut/native-range-map/

As settlers moved west across North America, they took chestnuts with them, and there are still healthy American chestnuts thriving in northern California, Oregon, and Washington, so chestnuts are certainly not restricted to their original range. (These areas are far enough from current blight infestations that they haven't been hit yet! There are strict import restrictions for chestnut trees to these areas to prevent the spread of blight.)


What parts of America are fit for chestnuts?

widowdogood


How well will it grow in mono type silviculture lands growing doug firs in the Pacific Northwest? Will these be sun loving or shade tolerant in a group? If your plans go well how long do you estimate before availability at regular nurseries?

Will they be resistant to ivy and other tree climbing weeds? What type of companion plantings go well with it?

MDCCCLV

See previous comment: https://www.reddit.com/r/science/comments/5zxa0e/science_ama_series_we_are_a_team_of_esf/df2cea0/

American chestnuts like well drained soil; they grow well in full sun and are moderately shade tolerant. I'm not sure about ivy and climbing weeds, but I don't think American chestnuts would be any more susceptible than other hardwood trees such as oaks. - Vern


I don't have anything to add, I just want to say thank you for your work. I'm only 30 but I remember chestnuts from my childhood, we had a tree in our yard growing up. I didn't know how special that was until I was older, and I have a tattoo on my arm of one now. I hope to see chestnut trees everywhere again before I am old.

ifyouhaveany

Us too! Thanks for the support!


Regardless, you'll be able to buy some seeds/cuttings?

hicaro20

We've added an answer to this in the introductory post at the top, but I'll just add that we're working hard to ramp up our production and optimize our propagation techniques so that we can meet the demand and get these resistant trees out to folks that want them! - Vern


First off great work. Most people don't even know about how popular chestnuts were or how common the trees were.

Have you found that this presents a barrier to reintroduction of the trees?

uber_neutrino

It's true that many people don't know about the history of this beautiful tree, but there are also many people who are very aware and dedicated to preserving and restoring the species - the American Chestnut Foundation has a strong base of members and supports our research. It helps how much our culture references the chestnut with street names and songs - people already feel some connection to the chestnut even if they don't know the whole story. Unfortunately, there are plenty of less charismatic species out there that are threatened by disease that don't get as much attention.


What climates are good for this tree? I'm in British Columbia, Canada.

rtfminc

(This is Andy) See previous reply: https://www.reddit.com/r/science/comments/5zxa0e/science_ama_series_we_are_a_team_of_esf/df2cea0/ Since there are American chestnuts growing well in Oregon and Washington, BC should be a reasonable climate! The bigger challenge might be finding/importing seeds or seedlings to plant, as you wouldn't want to bring in anything that might have been exposed to blight (from the original chestnut range).


Oregon State has done something similar with the Hazelnut trees, genetically modifying trees to be blight resistant. What are the similarities and differences between these solutions?

kikimonster

(This is Andy) From what I can see about OSU's hazlenut program, it's entirely a breeding program, rather than using genetic engineering as we've done with chestnuts. Hazlenut breeding would be more similar to the American Chestnut Foundation's breeding program, using traditional breeding techniques to (relatively) precisely select for desired traits in the next generation of trees. Traditional breeding always results in a mix of traits from both parents, so you can't predict beforehand exactly which traits will end up in the offspring. If you do enough crosses, you can often end up with good plants with most or all of your desired traits! This is essentially how we as humans have optimized agriculture over the past few hundred years to support our current population - breeding and selecting for productive and nutritious crops. But sometimes this can take many generations of breeding, which is especially slow for trees (which may take several years to mature between each generation). In contrast, genetic engineering allows us to make a very small, very specific change. In some cases this can be much quicker than breeding, and (based on experiments so far) it results in smaller changes as compared to hybrid breeding with a different species. But under our current regulatory system, genetically engineered plants in the US require approval from federal agencies before they can be distributed, which is complicated and expensive. We're working on it! But there are certainly pros and cons to both approaches, and they are not mutually exclusive.


Good for you. Please tell us more about the the steps to obtain federal approval for public tree sales and to introduce trees in the wild. What kind of political pressure can the public apply?

FernadoPoo

(This is Andy) Federal approval is different for each species, so it's hard to generalize! But basically all plants transformed with Agrobacterium (a natural soil bacterium commonly used to transfer transgenes into target tissue) must be regulated by the USDA-APHIS. They do a Plant Pest Risk Assessment and Environmental Assessment (or Environmental Impact Statement). Among other things, they need data to show that the new trait doesn't increase "weediness" of the plant in question. The EPA regulates anything that "mitigates" a pest - even though our transgene isn't a pesticide in the sense that it doesn't kill the blight fungus, we're still "mitigating" this pest, so the EPA has oversight. And the FDA is consulted any time the plant is eaten by people or pets/livestock. So in the case of chestnut, we're covered by all three agencies! The petitions include hundreds of pages of information, everything from detailed molecular characterization of what genes are nearby the transgene insertion site, to ecological effects on other organisms in the chestnut's range. An important part of our petitions will be explaining that the Oxalate Oxidase enzyme is already present in a variety of foods and native plants, so people already eat it (in unregulated quantities) and it's already present in the environment. While this is a new trait for chestnuts, it's not something foreign to our diets or our environment. As far as political pressure, one step would be to push for the continued integrity of the regulatory agencies! If budgetary measures force the USDA/EPA to significantly downsize, it might delay the regulatory process. Additionally, there are multiple Open Comment Periods during the regulatory process from USDA and EPA, where the agencies are seeking public feedback, especially for potential data points or important considerations that haven't yet been addressed. It would be extremely helpful during these open comment periods for the agencies to see that the public wants these trees! If you want to stay up to date on our work and find out when these open comment periods will happen, please join the Chestnut Foundation, support our fundraiser, and/or follow our FB page (links in OP). Thanks!


Do people get mad at you for making the trees "GMO"?

supermatthew

Rarely! (The vast majority of responses we see are positive, from people who want to plant blight resistant chestnuts! But there are some people who are hesitant for various reasons, and a small but vocal minority who are opposed to genetic engineering in any form. We actually hear from quite a few people who don't like genetic engineering as done by big corporations in agricultural crops, but they don't mind the idea of the technology being used to restore a threatened native tree.)


Can you share your research and help them fix banana's too?

greenSixx


One thing I've heard was that people were encouraged to cut down chestnut trees to not spread the blight but that it would have been better to not do this and see if any of the trees in the wild had a natural resistance. Is there any truth to this? Also, have we learned anything on how to deal with issues like this in the future with other plants?

Thank you all for doing such great research to bring a species back!

flynnguy

(This is Andy) Yes, it's true that early (1930's, IIRC?) efforts to contain the blight involved cutting down chestnuts. However, since the blight fungus can live on other species besides chestnut, this wasn't very effective! The process of cutting trees may even have spread blight, as the some pathogenic fungi can survive on saws, boots, etc. While it's theoretically possible that someone cut down a uniquely resistant American chestnut, this seems unlikely given the overall size of the American chestnut population, and the complete lack of natural resistance we've seen across the range.

We've certainly learned a lot about containing invasive species in general, and tree pests specifically! For example, there have been multiple introductions of the Asian Longhorned Beetle to the eastern US, but so far outbreaks have been small, they've been noticed quickly, and this pest has been basically contained (quarantines are in effect in Massachusetts). Further introductions or outbreaks are a constant threat, which is one reason why agencies like the USDA (specifically APHIS, who does this monitoring) are so important!


As I understand it, your team is trying to maximize the genetic diversity of your transgenic trees by inserting the oxalate oxidase gene into many different lines of American Chestnuts. Are you still in the process of doing this? If so, would it be useful to recruit people to send in tissue samples or suckers of native surviving trees?

Also, will you have to seek regulatory approval for every individual line of transgenic trees?... or is it possible to be granted approval for the process of inserting oxalate oxidase?

drz420

(This is Andy) We do ultimately want to maximize genetic diversity of chestnuts for restoration! But right now, we're only focusing on two lines. Our intent is that these lines can be outcrossed (or cross-pollinated) with a wide variety of locally-adapted chestnuts from across the native range. We already have "diversity orchards" of various lines of non-transgenic trees in permitted plots to start working on this as we get more pollen. We're also collaborating with the Chestnut Foundation, and other individuals who have orchards throughout the chestnut's range.
Rather than having people send in tissue of surviving trees, we encourage them to plant non-transgenic American chestnuts native to their local region, with the hope that they can be crossed with our transgenic trees when/if we receive regulatory approval to do so. This outcrossing will increase genetic diversity, and half of the offspring will inherit the transgene for blight resistance, making those offspring just as resistant as the original line we created in the lab. We do plan to seek regulatory approval for two (or possibly three) lines, but generally since these lines have the same genes in the same parental tree line, they can be combined into a single petition for each agency.


Do you think biodiversity helps to prevent invasive diseases or pests from doing so much damage as opposed to Planting a monoculture forest? What steps are being taken in the future to ensure diverse species plantings in the future. Thanks.

bizmarxie

(Vern here) Genetic diversity within a species is hugely important to its resilience in the face of insect pests and diseases, not to mention climate change. This is an example of how our restoration project is very different from genetic engineering in agriculture - our intent is plant a diverse population of regionally adapted trees by outcrossing with surviving wild trees throughout the range. See previous comment https://www.reddit.com/r/science/comments/5zxa0e/science_ama_series_we_are_a_team_of_esf/df2f5ea/


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