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Forest Health Roadmap Details


Forest Health Roadmap - Scope

The goal of this material is to support civil discourse and inform decisions about how to respond to current and potential forest health threats. The emphasis is on deciding if and how to intervene, with a focus on when genetic approaches to improving tree resistance might be appropriate to pursue. The roadmap might, for example, guide an analysis of research options for a public sector agency such as the US Forest Service, by a company considering the development and marketing of a transgenic resistant tree, or a certification or stewardship system deciding whether to endorse research or commercial deployment. Genetic options include conventional breeding and diverse biotechnologies, including genetic engineering. The threats to forest health of concern include biotic agents such as diseases and insects, and abiotic stresses such as climate shifts. Both exotic and native biotic agents, and the effects of variation in climate, are germane. A summary flow chart presents the general logical approach to decision making, but because of the complexity of forest-stressor interactions, general incompleteness of scientific understanding, and variable social perspectives on when intervention is appropriate, it is presented as a “guide or roadmap.” Accompanying material provides added explanations and examples to help inform the use of the roadmap in practice. Information supporting this process will come from a variety of sources including agencies, researchers, and other informed stakeholders.

This material is organized to first consider the state of knowledge and capacity about the forest health threat and tree genetic tools, second to evaluate the desirability of various kinds of breeding research, and finally to evaluate, if the research is successful, the desirability of release in wild or planted forests. This material scrutinizes transgenic tree research and release in depth.

Watch the FHI introductory video

Phase 1: Characterize the Threat

Characterizing the threat or creating a “dossier” of the threat includes documenting that a specific tree species is under threat, evaluating the level of threat, and delineating possible mitigation options. Viable non-genetic options, such as silvicultural practices or chemical controls, identified as part of Phase 1 should be pursued moving the user outside of the scope of the Forest Health Roadmap. If genetic options are to be considered the user of the roadmap moves to Phase 2 – Research.

ID Forest Health Threat

Document that a tree species is under threat. Some information sources include:
  • Finding by a USDA APHIS New Pest Advisory Group
  • Non-peer-reviewed agency fact sheet (federal or state)
  • Peer-reviewed publications
  • Fact sheets issued by university extension services or similar entities
  • Specialist network recommendations & social networking hub

    • Note: A non-native pest is defined as any species not native to the ecosystem under consideration (Executive Order 13112)

    Evaluate the Damaging Causal Agent/s and/or Conditions

    Evaluation of threat level. Points to consider include:
    Importance of the tree species to:
  • Natural ecosystems
  • Horticulture/urban forests
  • Wood products or other economic returns
  • Stage of tree damage or death
  • Does the rate of tree damage or death matter in this species?
    - If so does damage or death of individual trees occur rapidly or over a period of years?
  • Early stage where rapid action could prevent loss of the species in parts of the range (e.g., thousand canker disease in walnut)
  • A significant reduction in the species’ numbers/presence, but not complete ecological extinction
  • Virtually eliminated from large parts of its range (e.g., American chestnut)
  • Rapidity of pest’s spread
    - Spread by natural means (flight, wind) or largely assisted by human activities (transport in firewood or nursery stock)?
    - Are significant populations of vulnerable species separated by distance and unsuitable habitat from the principal outbreak?
    - Are programs in place (or likely to be implemented) that show promise for slowing the pest’s spread such as federal or state quarantines, voluntary industry practices, measures for sanitizing pathways of movement?

    • Delineate Mitigation Options

    Non Tree Genetic Options
    Pest suppression efforts to consider include:
  • Traditional silvicultural practices such as thinning, site preparation, prescribed burning, etc.
  • Chemical controls
  • Biological controls including pest mating disruption
  • Quarantine strategies
  • Traditional forest practices such as culling diseased trees that can lead to genetic changes if resistance is heritable


    • Phase 2: Research Different Options

    For all breeding options, consider technical feasibility, social interests, and ecologically beneficial and adverse effects. Conduct research and re-evaluate all of the above and their interactions as ecosystems and societies change over time. Choose to continue, or discontinue additional research and move projects to release options. If Research Phase determines biotech trees should be pursued, move to Phase 3 – Pursue Biotech Tree Solutions.


    Breeding Strategies

    Evaluate Traditional Breeding Options
  • Does native pest/disease resistance exist?
  • Is there an exotic source of resistance? (hybrid breeding)
  • What is known about the heritability of resistance? (If dominant resistance is present in native population this would be compelling reason to go the traditional breeding route)
  • What is known about durability of resistance?
  • Is there a need or a way to incorporate multiple resistance genes, pathways?
  • What is known about genetic gain?
  • If the trait is complex, is there a genetic model? How many generations of crosses are required to achieve final product?
  • Is there an ongoing breeding program? If so, at what phase is this program? Selection of resistant parents? F1 crosses? Advance pedigrees? Material available for deployment?
  • Is provenance data available?
  • What is known about genetic variation in the species & is there a plan to incorporate this into the breeding program?

    • Recommendations:
    - Identify breeding experts and programs that work with this species or forest health threat

    Evaluate Traditional Breeding with Biotech Assistance
  • Are mapping families available?
  • What sequence information is available?
  • What kind and how many markers have been developed for the species?
  • Are markers from closely related species transferable?
  • Is a linkage map available?

    • Determine which of the following approaches are contemplated or under way and fill the gaps
  • Conservation of genetic diversity of the tree species through ex situ or in situ methods
  • Attempts to locate and screen putatively resistant trees
  • Research on possible resistance mechanisms in host trees in the pest’s native and invaded environments
  • Gene sequencing of hosts


    • Evaluate Transgenics

    Transgenic technology status
  • Is a transformation/micropropagation system, needed for production and propagation of the transgenic trees, available and/or feasible to develop?
  • What is known about the function of the proposed transgene? Is there genomic, proteomic, or metabolomic information available that might help to evaluate the extent of physiological changes induced?
  • How precise is the genetically engineered trait? For example, are promoters identified with known tissue specificity, and is that specificity known to be retained in the transgenic trees?
  • How stable is the transgene, both in physical structure and expression? Is it as expected over tree development and under environmental variation?
  • If multiple resistance transgenes are involved, what is known about the physiology and role of each gene? Are the genes added within an already partially resistant genotype to provide a broader base of resistance?
  • Have research field trials been conducted in a reasonable sample of target growing environments? Has the target abiotic and/or biotic stress agents been adequately sampled?

    • Business/social environment
  • Are there public sector institutions or private companies with the intellectual capital, laboratory and facilities, and financial resources to develop marketable transgenic trees?
  • Is enabling technology (e.g., genes, promoters, selectable markers, in vitro culture and gene insertion methods) and associated intellectual property for producing regenerated transgenic trees available and affordable?
  • Is the field trial data in hand, or that can be affordably obtained, of sufficient quality for regulatory agencies? Do they include comparators, such as conventionally bred varieties of the same species and conventional silvicultural practices, so that ecological impacts can be meaningfully compared and evaluated?
  • Is there a socially approved stewardship plan in place, such as by following the Responsible Use program of the Institute of Forest Biosciences?
  • Is there a sustainability certification program in place or that can be developed that will accept and approve the transgenic trees?
  • Is there a market that will use or purchase the transgenic varieties? Can this be developed while the transgenic trees are being sold and grown?
  • Is vandalism against field sites or plantations expected from strongly opposed groups? How can this be avoided or managed? Is there a likelihood of strong social and/or legal resistance from companies, NGOs or citizens opposed to use of the transgenic trees, for example by demonstrations, boycotts, or lawsuits?
  • Are the transgenic trees of high social value, such as for a restored keystone tree species or for a highly productive and stress-tolerant, but contained, bioenergy species?

    • Biological/ecological impacts
  • Have pleiotropic (unexpected) effects been examined, for example that might impair tree fitness under stress or harm non-target organisms? Have the effects of the transgenes on ecological characteristics been studied, such as allelopathy (soil-based toxicity to other plants), soil biogeochemistry, and toxicity to non-target organisms that naturally feed on trees or live in soil under them?
  • Has the genetic diversity of the trees been substantially reduced as a result of use of transgenes, for example by deploying only one transgenic clone over a wide area?
  • What is known about the potential for spread of the transgene via gene flow? Is extensive spread likely and desirable? Is it possible that progeny of the transgenic tree will be able to outcompete other species and become a serious invasive pest? What is the frequency of transgene spread into related wild and feral species that is expected? If sexual reproduction is allowed or expected, is there a chance of hybridizing with native species? Is this considered a hazard or benefit?
  • What is known about reproductive biology of target pests? What is the risk of the target pest developing resistance to transgene, e.g. Bt toxin, and how will it be managed?
  • Are the transgenes familiar or highly novel in their gene products? Is the stress-tolerance promoting gene the same (cisgenic) or nearly the same in coding region but with differing expression (intragenic) relative to genes in the gene pools of sexually compatible wild relatives? If the genes are from species that are not interfertile or the genes have been extensively modified by synthesis, are they highly homologous in protein sequence to that of native genes (i.e., can be considered genomic guided transgenes (GGTs: Strauss 2003)). Have the accessory genes and other elements, such a promoters, terminators, and selectable markers, already obtained regulatory approval and been in wide and safe use in other transgenic crops?

    • Phase 3: Pursue Biotech Tree Solutions

    Research & Development

    Biotech Research

    The biological science component of the Forest Health Initiative (FHI) supports core activities needed to promote the health and/or restoration of threatened forest tree species. The first target species, American chestnut, was almost lost from its former range by introduction of an exotic fungal pathogen that causes chestnut blight. Over the past fifty years, many public and private organizations, motivated by concerned citizens throughout the U.S., have tried to restore the American chestnut to its former status in the Eastern hardwood forest. These activities, usually involving selection and breeding or attempts to attenuate the pathogen, have not yet achieved success. FHI is building on these past efforts, introducing new biotechnology tools and knowledge not previously available, and serving as an integrated platform to accelerate species restoration.

    American chestnut restoration presents enormous challenges. Conventional backcross breeding programs introduce blight resistance from related species, followed by crossing of hybrid offspring to recover resistant and nearly pure American chestnut trees. These programs require many years of effort for each breeding cycle. Similarly, reliable blight resistance screening requires many years for trees to reach appropriate size for inoculation and genetic screening.

    How is FHI contributing? Transgenic technology is rapid in that it requires no breeding, and is precise in that the immediate product is a nearly pure American chestnut genome. However, there are still knowledge gaps regarding the most appropriate transgenes to introduce that will improve resistance to chestnut blight. Advanced marker-informed breeding and selection may prove successful, but it is not known whether and how genome rearrangements between donor species and American chestnut may affect efficiency of backcross breeding. Additional knowledge gaps surround accurate rating of heritable blight resistance in very young seedlings. To fill these gaps, FHI is supporting the discovery of genes and their organization from blight resistant species and hybrids through genome sequencing and DNA marker development, thereby creating platforms for accelerated breeding strategies and for evaluating candidate transgenes. FHI is also supporting the development of early, accurate blight resistance screening protocols in vegetatively propagated material.

    The activities of this biological research component of FHI is reinforced by parallel activities focused on social, environmental and policy aspects, in order to engage the broad communities demanding options for restoration of American chestnut.
    Download the FHI Research Flowchart

    Social & Ethical Considerations
    Click on the blue links to download documents.
    Goals of this working group are to develop broad social and environmental stakeholder understanding on how biotechnology may be used to preserve and restore forest health. Much like the broader FHI, the Social Environmental Group (SEG) has embarked on a three-pronged, parallel and fully coordinated (braided) approach to achieving its goal.  The three Work Groups of the SEG were established as follows:

    • Issues Work Group: addressing key questions, issues and concerns by stakeholders.
    • Principles Work Group: indentifying and integrating principles for responsible deployment of biotechnology to address current and emerging forest health threats.
    • Outreach & Communications Work Group: developing and executing a plan to solicit broad input and engage key stakeholders that result in broad stakeholder understanding and acceptance of the FHI. Watch the FHI introductory video
    Regulatory Roadmap

    Click on the blue links to download documents.
    The Policy group of the FHI investigates how to best navigate the regulatory processes in place in the U.S. that govern the use of a biotech tree that is by design intended to flower and propagate in the open forest. In this potential scenario a genetically engineered American chestnut would be regulated by three U.S. agencies:

    1. U.S. Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) regulates all genetically engineered organisms that could affect agriculture or the environment. All biotech trees are regulated by APHIS.
    2. U.S. Environmental Protection Agency (EPA) regulates uses of Plant-Incorporated Protectants (PIPs) for safe use in the environment. All biotech trees that are resistant to viruses are regulated by the EPA.
    3. U.S. Department of Health and Human Services’ Food and Drug Administration (FDA) regulates all human food and animal feed additives. Genetically engineering a food product is considered to be a food additive to the FDA. All biotech trees that produce human food or animal feed are regulated by the FDA.

    While this specific application of biotechnology is intended purely for environmental and societal benefit, it does not change the fact that these agencies are designed, and required, to respond to actionable items. In other words, agencies that regulate need some thing to regulate. However, there may be no actionable item (a biotech tree) for years. The Policy group’s task was to work within these systems to gather information that may help speed regulatory determinations.

    The Policy group collaborated with the entire FHI and the three aforementioned agencies to develop the response plan for using advanced biotechnology as a tool for forest health. 

    Navigating US Regulations on Forest Biotechnology Research


    Environmental Research

    Click on the blue links to download documents.
    The goal of this document is to outline how to scientifically assess the ways and extent to which a transgenic tree (modified by genetic engineering methods) has impacts on the physical and biological environment. It includes examples of how assessments for transgenic trees might be done, and experiences from agricultural biotechnology. Assessments should consider expected direct and indirect impacts, as well as to search for unintended effects of transgenic modification. Important expressions to consider include effects on non-target organisms, soil nutrition and toxicity, and the ability of trees to compete and disperse. All assessments should include field-based comparisons to contemporary forestry practices, such as conventional breeding, planting, and harvesting, so that the relative magnitude of impacts can be determined.

    Synthesis of American chestnut (Castanea dentata) biological, ecological, and genetic attributes with application to forest restoration

    Biotech Tree Trials

    Intellectual Property Review

    Ms. Lori Knowles of the Health Law Institute in Alberta, Canada was commissioned to perform an intellectual property (IP) review on the potential use of certain genetic constructs in the biotech American chestnut. The goal of this review is to allow the FHI science teams to gain a better understanding of the direction research in the field is moving, who is conducting that research and where that research is being conducted. In addition, the IP study will identify parties who hold relevant intellectual property and identify opportunities for the creation of strategic relationships or negotiations with patent holders.

    Go to FHI's list of research reports.

    Term Definitions

    • Traditional breeding: purposeful sexual propagation of trees involves producing progeny of parents from different genetic populations, to create a desired phenotype.
    • Clonal propagation: asexual propagation producing genetically identical trees using methods such as grafting, rooted cuttings, tissue culture, or somatic embryogenesis.
    • Marker aided selection/breeding: with information about a tree’s genome, molecular markers can be used to locate specific genes in potential seedlings, at an embryonic stage. These landmarks in the genome give breeders the advantage of speed and accuracy in a breeding program.
    • Interspecific hybridization/breeding: purposeful sexual propagation of trees between species.
    • Transgenic research: genetic engineering is an advanced science in which DNA sequences encoding for very specific and desired traits are introduced into the plant's genome.