Darling 58

A “wild-type” American chestnut tree is one that has not been intentionally hybridized with other chestnut species. Because these trees are open-pollinated, seedlings from wild-type American chestnuts may have been naturally pollinated by other chestnut species. TACF can offer no guarantees, but to the very best of our knowledge, our wild-type seedlings are American chestnuts.

TACF’s seed sponsor program distributes the best performing lineages of disease-resistant American chestnuts available. These seeds are primarily sourced from TACFs backcross seed orchards at Meadowview Research Farms and the Arboretum at Penn State. Resistance is not guaranteed, but the parents of the seed/seedlings have been tested to have measurable blight-resistance above wild-type American chestnuts.

Eventually, upon regulatory approval and under formalized agreements with SUNY-ESF, TACF intends to integrate D58-based materials into this program. 

Visit the seeds & seedlings page for more information about how to get American chestnuts from TACF.

There are a few ways that you can support American chestnut conservation and restoration. You can become a member of The American Chestnut Foundation. You can also plant wild-type and/or backcross American chestnuts to participate in our tree breeding efforts as a citizen scientist.

We are continuously studying interactions between our transgenic trees and the environment and potential impacts on ecosystem and human health. A series of articles summarizing various safety tests relevant to the regulatory process were published by The American Chestnut Foundation (read about Nutrition, Wildlife, Plants & Fungi).

People with celiac disease or other forms of gluten intolerance can eat nuts from Darling 58 chestnuts safely. The OxO gene in Darling 58 is not related to gluten and is also found in many gluten-free grains and other foods (sorghum, rice, bananas, etc.) that are regularly consumed by celiac patients. ESF used the amino acid sequence (specific arrangement of the protein) to screen against a large database of known toxins and allergens as well as theoretically predicted ones, both resulting in no matches. In addition, Darling 58 chestnuts have been tested by a commercial testing lab for both wheat allergens in general and gluten specifically. Those tests all came back negative.

No, Darling 58 American chestnuts are not hybrids. They retain a majority of the background tree into which they are bred, along with an extra gene, OxO, which confers some amount of blight tolerance. Hybrid chestnuts, like those produced through The American Chestnut Foundation’s backcross breeding program, are a cross between Chinese and American trees. Chestnut species freely hybridize and other hybrid varieties exist. Crossing D58 with both backcross trees and wild-type American chestnuts will be an essential part of utilizing this product for ongoing species restoration efforts.

The Darling American chestnut was named after Herb Darling, the founder of the New York Chapter of TACF. Herb, along with Stan and Arlene Wirsig, were the people who approached Dr. William Powell and Dr. Charles Maynard, the co-founders of this project, back in 1989 about taking a biotech approach to develop a blight-resistant American chestnut tree. Herb Darling was instrumental, providing the project with original funding and supporting ESF through the NY-TACF Chapter for the next 25 years.

APHIS – Animal and Plant Health Inspection Service – A unit of the U.S. Department of Agriculture responsible for protecting animal welfare, animal health, and plant health.

Backcross breeding – a technique to develop disease resistance wherein American and Chinese chestnuts are bred together and their progeny are bred with American chestnuts to produce a mostly American chestnut with traits of resistance

B3F3 (or similar conventions) – common nomenclature to refer to 7th generation backcrossed progeny of American and Chinese chestnuts by TACF

BRAG – Biotechnology Risk Assessment Grant – A funding program of the U.S. Department of Agriculture’s National Institute of Food and Agriculture intended to support generation of scientific evidence needed to assess affects of introduction of genetically engineered organisms

CRISPR – Clustered Regularly Interspaced Short Palindromic Repeats – a technique for gene editing and insertion

Cryphonectria parasitica – The scientific name of the fungus that causes chestnut blight

Common garden experiment – A type of experiment used to compare how organisms from geographically or environmentally distinct sources respond to living and growing in the same environment. This helps parse their apparent differences into those driven by genetics and those driven by their environment.

D58 – Darling 58 – transgenic variety of American chestnut developed at SUNY-ESF

DarWin – Darling with Wound Inducible promoter. A transgenic chestnut tree which expresses the same OxO gene as D58, but only when wounded and only at the site of wounding. A recent development by the Powell lab at SUNY-ESF

Deregulation – the current process of submitting appeals to the USDA, EPA, and FDA to allow wider dispersal and expanded trials of the transgenic D58 chestnut tree

EPA – Environmental Protection Agency

FDA – Food and Drug Administration

FHI – Forest Health Initiative

GCO – Germplasm Conservation Orchard – an orchard where seeds from wild-type American chestnuts are planted to preserve their genetic diversity

Hypovirulence – a phenomenon wherein the blight fungus is weakened by infection with a virus. Depending on the interaction and relative virulence of the fungus and virus, the fungus may exhibit slower growth, reduced virulence and overall reduction in fitness.

MOU – Memorandum of Understanding – an agreement between TACF and a partner organization which documents the goals and general terms of that partnership

OxO – Oxalate oxidase – The terms commonly applied to a gene which produces the enzyme oxalate oxidase, which neutralizes oxalic acid. In American chestnut restoration context, the OxO gene is one of the most promising to confer resistance to the chestnut blight fungus.

PRR – Phytophthora root rot/ink disease

Phytophthora cinnamomi – the scientific name for the organism which causes Phytophthora root rot

Pure/purity – a commonly misconceived quality attributed to wild-type American chestnuts. All chestnut species have experienced hybridization events

Reciprocal transplant experiment – A set of replicated common garden experiments where organisms from all source populations are compared in each other’s and in their own habitats of origin. This helps uncover whether particular populations are well adapted only to their own habitats or in other habitats as well.

RNAi – In the context of American chestnut restoration, this is a method whereby partial sequences of important pathogenicity genes from the chestnut blight fungus are inserted into American chestnut. The partial fungal sequences are expressed in the chestnut tree as double stranded RNA, which are then degraded by the chestnut trees through a pathway called RNA interference. The degradation of the key fugal pathogenicity genes by the host reduces the chestnut blight fungal virulence. Thus far ESF researchers have used this technology to silence chestnut blight genes involved in the production of oxalic acid, which reduces the chestnut blight fungus’s ability to kill tissues in chestnut bark.

ROC – Regional Outreach Coordinator – employee of TACF responsible for oversight of chapters and volunteer initiatives in their respective region

RSC – Regional Science Coordinator – employee of TACF responsible for oversight of scientific endeavors in their respective region

RSC – Resistance Screening Center – a US Forest Service facility at Bent Creek Experimental Forest, Asheville, NC

S&T – Science & Technology Committee of the Board of Directors of The American Chestnut Foundation.

SSA – Small stem assay. An inoculation trial performed on seedling trees wherein the pathogen is artificially administered in order to compare differences in apparent response for early screening of disease resistance.

Stacked resistance – a technique utilizing the best progeny of the backcross breeding program to then cross with transgenic American chestnut to yield an offspring with resistance characteristics from both techniques

SUNY-ESF – State University of New York College of Environmental Science and Forestry
Transgenic – modification of an organism using an inserted gene that comes from a different organism that is not sexually-compatible with the target organism

TACF – The American Chestnut Foundation

USDA – United States Department of Agriculture

Wild-type American chestnut – a tree which is either a member of the remnant population of American chestnuts in the wild, or progeny thereof.