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The American Chestnut Research
Progress Updates 2023

ESF Darling Chestnut Science Summary

Access our summary page that includes summaries of scientific studies on Darling 54 chestnuts.


ESF Continues Promising Development of Darling Transgenic Chestnuts 

The American Chestnut Research and Restoration Project team remains committed to chestnut and tree restoration research, building off nearly 35 years of dedicated work and study. Our research so far indicates1 that Darling chestnuts are safe and have better blight tolerance than other American chestnuts, so they can play an important role in laying the groundwork for restoration of threatened populations of American chestnut trees. In November, we received a $636,000 grant from the USDA’s National Institute of Food and Agriculture’s (NIFA) Biotechnology Risk Assessment Grants (BRAG) program. It will be used to monitor the dispersal, fitness, and deployment of the genetically engineered American chestnuts developed by ESF researchers, including Darling trees. Furthermore, ESF is in the process of hiring a five-person faculty/staff cluster in "Tree and Ecosystem Restoration” to help bolster our expertise, expand restoration beyond chestnut, and strengthen our team of scientists.  

ESF has been the leading academic institution on biotechnology for enhancing blight tolerance in American chestnuts, and we look forward to continuing that role in which we take great pride and responsibility.  

We will be sharing links to documents about our research and data on this page. But first, we’d like to provide some clarification:  

  • Multiple approaches are needed to address chestnut restoration. No single chestnut variety will fully address American chestnut restoration; it will be a gradual process of discovery, implementation, and improvement. We are confident that Darling trees represent a valuable first step, and further research will help clarify which varieties are most suitable for large-scale restoration. 
  • There was an identity error of the Darling 58. We discovered recently that an unfortunate labeling error occurred several years ago between two Darling varieties (54 and 58) that were developed at the same time. We are fixing the labeling, amending the filed documents within the regulatory approval process, and working to understand how it happened. 
  • Extensive testing has been done on Darling 54. The difference between Darling 54 and Darling 58 is the location of the new transgenes; the OxO gene is the same but located on a different chromosome. Data we have already provided to regulatory agencies confirms safety and characteristics of D54. 
  • ESF is continuing to pursue the regulatory approval process. We have no indication that new data will result in safety concerns that could jeopardize regulatory review. Following draft decisions published last year, the USDA-APHIS expressed no indication that OxO or the Darling variety might be harmful to the environment, ecosystems, or people. We are following agency guidance for submitting updates, but do not intend to withdraw the petition.  
  • The Darling variety does not exhibit major performance risks. Initial field trials indicate that blight tolerance is consistently enhanced in Darling trees compared to closely related controls without the OxO gene. Overall, Darling trees are shorter than their non-transgenic relatives, but height varies within and among families. These trees, both OxO positive and negative, will continue to be monitored over the long term. Regulatory approval will allow for even more rigorous evaluations of suitability for eventual large-scale restoration work. 
  • Research must continue. Testing is an important first step for large-scale restoration and we will continue to plant, watch, and collect data. We’ve done extensive health and safety testing of the Darling variety in support of our regulatory filings and every indication to date is they do not pose harm.    

Our data and observations1 so far indicate that potential restoration plantings will help conserve existing populations of American chestnut trees without causing harm to the trees or their habitat. Blight tolerance in Darling chestnuts is consistently enhanced compared to wild trees, so this represents an important milestone toward restoration of trees threatened by invasive pests and pathogens.  

The team of scientists with the American Chestnut Research and Restoration Project continue to prioritize rigorous science and discovery before large-scale restoration, and regulatory approval will facilitate research plantings to help the restoration community make those decisions. We’re all proud of the work that Dr. Powell and his team have done, and we look forward to continuing his legacy. 



December 2023

ESF remains committed to chestnut and tree restoration research. We are continuing to pursue approval from federal agencies and work with regulators, and reviews remain underway.

We continue to prioritize rigorous science and discovery in our long-term goal of safe and effective forest restoration. Our research so far indicates that potential restoration plantings will help conserve existing populations of American chestnut trees without causing harm to the trees or their habitat. Several tools and approaches are needed to adequately address chestnut restoration, and we are continuing work on Darling, DarWin, and other varieties to find the best path forward for chestnut restoration.