Support the Restoration of the American Chestnut

6 min readOct 16, 2020

This comment has been submitted to the petition for the approval of the chestnut in the APHIS system. But it might take a couple of days for approval, and the comments close this coming Monday, October 19 2020. If you care about this project, comment by then. It does not need to be a lengthy comment, but this is a project I’ve followed for years and wanted to capture many features of it. More guidance on comments from the chestnut researchers here.

Post your comments to the federal system here:

I write to support the granting of the petition for the Darling 58 American chestnut Castanea dentata (and its offspring) to be considered nonregulated by APHIS because it does not pose a plant pest risk. The full submission document provides appropriate and convincing scientific evidence that this bioengineered tree does not pose any greater risk than its isogenic controls or those of traditionally bred chestnut varieties.

Rescuing the remaining wild American chestnut trees with this single insertion is a wonderful way to accomplish an ecological restoration for these trees to their former important place in our forests. These trees retain 100% of their original gene complement, and merely get help from one enzyme to become tolerant to blight.

TACF has a helpful page with links and details about the public comment period. It ends MONDAY OCT 19.

The research team has provided sufficient evidence about the characterization of these trees from molecular and ecological perspectives. Most of this is straightforward and conventional biotechnology and environmental science, and will not raise concerns among people who understand the scientific issues.

I will speak to the science on one of the topics, though, as it seems to be a source of public confusion, based on my reading of other comments here. There are concerns about the durability of the choice of blight tolerance and the oxalate oxidase (OxO) system that is being employed. While anti-GMO activist groups are posting a copy/pasted comment about OxO that they don’t understand, in fact they are being misled by opponents of this project. The oxidase system is, in fact, a clever and likely more durable and sustainable strategy than some others might have been.

Anti-GMO activists are flooding the comment system with copy/paste claims they don’t understand. Please bring science to the comments.

As the project researchers describe, this gene was selected because it can reduce the harm of the blight organism, but specifically does not kill the fungus. This should reduce the likelihood that the fungus will ramp up its own defenses and mutations to overcome the tolerance. In addition, because of the nature of the single construct involved, half of all the offspring of this tree will be wild-type chestnuts without the blight tolerance. These trees are carrying their own “refugia” strategy much like that recommended for Bt maize. This is a wise method to preserve the effectiveness of the tolerance system. Every generation will also produce non-transgenic offspring, which might even give those trees a chance to adapt to changing climate and other threats going forward.

At the same time, this OxO gene is present in many other organisms, regularly consumed by humans and other species already, and does not pose a risk of novelty. In summary, OxO is a wise choice as it is widely present already, and demonstrates no adverse effects on health or the environment.

Simultaneously, these trees will bring great benefit to the restoration of forests in multiple ways. Besides being long-lived storage for carbon that brings climate benefits, making the flowers and nuts available to forest species is a tremendous opportunity. “Pre-blight American chestnut has been described as “the most important wildlife plant in the eastern United States” (Davis, 2005).” Loss of this tree likely had impacts on birds, mammals and insect species as well. Researchers note that some species that used to rely on these trees may already be functionally extinct, sadly, but maybe they can recover if we do this in a timely manner. Some, like bumble bees, might specifically thrive with access to these flowers.

Again, to the timeliness of this, we currently have a small number of existing chestnuts that survived blight. While those trees still exist, they can be deliberately used to enhance the population diversity of the rescue trees. If we wait much longer, this might not be the case. Further, many forests still have chestnut root systems with the native organisms that support these trees. While those exist, we should ensure the new trees have a chance to access these soils and their microbiomes.

Tests of the plants and their sequences were appropriately performed to include the mycorrhizal colonization of chestnut roots, impacts of herbivory, leaf litter, and on pollinating insects as well, with no difference from wild type or traditionally bred chestnuts. Environmental studies indicate that this is not an environmental plant pest risk.

Besides being convinced that the science is properly conducted by the researchers, there are aspects of this project from a social and cultural perspective that are really unique and important. In the proposal, I was surprised to learn about an aspect of the project that I didn’t know: this whole chestnut program was on the impetus of “chestnut enthusiasts”. It was not from the scientists — they came in to support the idea after it came from the public. This may explain the heartwarming and large outpouring of support for this program from the public.

APHIS petition for GMO chestnuts reports that the project came from the public.

The not-for-profit distribution plan for these non-patented trees should allay the fears of those who falsely claim this is some kind of industry program. And even I, as a scientist, was charmed by the non-science public comments I had already seen that included the span of generations — people spoke lovingly of grandfathers who told them stories of chestnut trees or built barns or furniture that is cherished by the family, and how they want to plant their own trees on their own land for their grandchildren to enjoy. The excitement for planting these magnificent carbon sink trees by citizen scientists is a valuable aspect of this program as we wish to encourage people to fight climate change. Many people said that they had heard about the plight of the chestnuts in school and were pleased to know that science has progressed to restore them. This is an excellent way to demonstrate to people that science can deliver solutions to problems of our environmental damage.

The long-standing active and far-ranging outreach program by this team has also been effective and crucial. Impressive efforts including outreach to Native American groups to explain the project and to encourage involvement in restoring the tree to the original lands are underway. A tree that was previously available and important to native peoples was lost by later settlers’ activities — this is a way to make some amends for that.

The American Chestnut Foundation (TACF) non-profit program offers well-positioned support and structure to carry out the public facing components of the ongoing proposed research and distribution.

In short, the solid science as well as the social and cultural aspects of this project make this an excellent opportunity for ecological restoration and do not pose plant pest risks. They offer plant benefits in many ways.




Mary Mangan PhD is a genomics scientist, with credentials in microbiology, immunology, plant cell biology, and and molecular biology.