Agarikon (Fomitopsis officinalis), a medicinal fungus that grows almost exclusively in old-growth forests of northwestern North America, the Alps, and northeastern Eurasia, is facing habitat loss and extinction as old-growth timber is harvested. Mycologists can preserve the genetic diversity and unique medicinal properties of individual Agarikon strains by extracting a small tissue sample from a wild fruiting body using a cork borer, culturing it through successive generations of petri dishes, and then banking the mycelium in test tubes under refrigeration or liquid nitrogen. This cloning approach captures the exact phenotype and genetic material of each strain without damaging the wild organism, allowing researchers to preserve mycodiversity for genomic analysis and future medicinal discovery.
Why Is Agarikon Conservation Urgent?
Agarikon is a polypore mushroom that fruits exclusively in old-growth forests—ecosystems increasingly cleared for logging. The fruiting bodies, called conks, are substantial woody structures that can take decades or centuries to develop on large trees. As old-growth forest habitat disappears across North America, Europe, and Asia, populations of Agarikon are shrinking, and many unique genetic strains are lost before they can be studied. Agarikon is now considered a threatened species in Europe. Each wild population represents a distinct genetic lineage with potentially unique medicinal properties—properties that cannot be recovered once a strain is extinct in the wild.
The conservation challenge is not simply about protecting the species in aggregate, but about preserving mycodiversity: the genetic and phenotypic diversity within the species. Different strains of Agarikon have been observed to exhibit varying potency in their anti-inflammatory, antiviral, and immunomodulating properties. By collecting and culturing as many genetically distinct strains as possible, researchers can preserve this internal diversity and eventually analyze each strain's unique biochemical profile.
What Is the Cork Borer Technique?
The first and most critical step in Agarikon cloning is the field collection. Rather than harvesting the entire fruiting body (which damages the ecosystem and removes the organism), mycologists use a cork borer—a hollow cylindrical tool with a threaded screw inside—to extract a tiny piece of tissue from the hymenial (spore-bearing) layer on the underside of the conk. Stamets emphasizes that the incision should never penetrate the tough outer cuticle on the top surface. The analogy is precise: "It's like putting a hole in a tortoise shell," which creates a cavity vulnerable to water infiltration and wound infection that can kill the fruiting body. Instead, the cork borer accesses tissue from underneath, a method that allows the wound to heal naturally and invisibly over time.
The cork borer is first soaked in isopropanol or ethanol to sterilize it. Once a suitable conk is located—ideally one that is healthy and actively producing spores, not already decomposing—the borer is pressed gently into the hymenial surface just below the porous layer. A small cylinder of tissue, no more than a few millimeters in diameter, is extracted and placed immediately into a sterile plastic bag for transport back to the laboratory. The remaining fruiting body is left untouched to continue living and sporulating.
How Does Tissue Culture Convert Field Material into Culture Stocks?
Once the tissue sample arrives in the laboratory, the mycologist must move quickly to prevent contamination by competitor organisms—molds, bacteria, and saprophytic fungi that colonize dead wood faster than Agarikon mycelium can grow. The tissue fragment is placed in a sterile environment with sterilized tools: scalpels, petri dishes, nutrient media, and cloth, all of which have been autoclaved (pressure-cooked) beforehand.
Using a sterile scalpel, the interior flesh of the tissue is exposed—accessing the living mycelium inside the conk wall—and tiny fragments no larger than a grain of rice are cut and placed onto the surface of nutrient-filled petri dishes. Stamets notes that the success rate is "extremely high" in terms of potential failure: "The potential for this not to go as planned is extremely high." Of ten fragments plated, typically only two or three will successfully establish and grow mycelium across the agar surface. This is the first-generation isolation, or P0, the direct culture from wild tissue.
Several weeks later, once the mycelium has colonized a petri dish completely, portions of that vigorous mycelium are carefully transferred into fresh petri dishes using sterile technique. This second-generation culture, called P1, is now one step removed from the original field sample and is more likely to be axenic (free of contaminants). One or two of the cleanest, most vigorous P1 plates are selected and subcultured again into P2 plates. This progressive selection and amplification isolates not just a living culture, but the genetic clone of the original wild fruiting body.
What Does Banking a Strain Mean?
Once a stable, contamination-free culture has been established through multiple generations of petri dishes, the mycologist moves to the banking phase: preserving the strain in a form suitable for long-term cold storage. The mycelium from a fully colonized petri dish—the most vigorous and best-looking growth—is transferred into sterile test tubes filled with the same nutrient medium. Stamets uses two sizes: larger master tubes for long-term backup culture and smaller secondary tubes as additional insurance against loss.
The inoculation of test tubes requires strict aseptic technique. The petri dish lid is removed, and a scalpel is used to cut away a generous piece of living mycelium. The test tube cap is loosened slightly (to allow mycelium to access oxygen), and the mycelium is carefully deposited inside and allowed to grow across the surface of the medium. Stamets employs a clever trick: he allows the mycelium to grow to a stage where it begins to creep down the sides and underneath the glass surface of the test tube. If the culture is stored in refrigeration for years or even decades and the surface mycelium dies back, the living mycelium beneath the glass can be revived by smashing the tube, exposing the subsurface growth, and reculturing it into fresh medium.
Once the test tubes are fully colonized, they are sealed with parafilm (a breathable wax film) and moved into cold storage—a standard refrigerator set to a few degrees above freezing. At this temperature, mycelium metabolism slows dramatically, and the culture can remain viable for years or even centuries with minimal maintenance.
How Does Liquid Nitrogen Improve Long-Term Banking?
For the most durable long-term preservation, mycologists also prepare samples for storage in liquid nitrogen, a cryogenic technique that can preserve living cells in a metabolically inert state indefinitely. While Stamets mentions this only briefly in the video, it is a recognized backup protocol: test tube cultures are supplemented with cryoprotectants (usually glycerol or DMSO) and small aliquots are transferred into sterile vials, which are then slowly cooled and plunged into liquid nitrogen at −196°C. At this temperature, all biological activity ceases, and the culture remains unchanged for decades or longer. Should a refrigerated culture be lost to contamination or equipment failure, the liquid nitrogen archive serves as a genetic insurance policy.
What Happens After Banking?
The banking process is not an endpoint; it is a staging point for research. Once a strain is safely preserved in culture, it becomes available for multiple downstream applications. Stamets and his team at Fungi Perfecti have built a collection of 72 Agarikon strains—the largest in the world—and are engaged in a large-scale genomic and biochemical study comparing the strains' properties. The goal is to reach 100 strains and perform DNA sequencing on all of them to identify subclades (genetically distinct lineages within the species) and correlate genetic diversity with variation in medicinal activity.
Early results already show that different strains have markedly different potencies for anti-inflammatory, antiviral, and immunomodulating effects. Some strains appear to be significantly more bioactive than others. By having many strains in culture, researchers can grow fresh mycelium or fruiting bodies of each strain, extract their compounds, test them in laboratory and clinical settings, and build a comprehensive understanding of what makes individual strains valuable. This knowledge can then guide future conservation priorities in the wild: protecting not just Agarikon as a species, but protecting the genetic lineages most likely to yield new medicines.
How Does Cloning Differ from Spore Cultivation?
A cloning approach via tissue culture differs fundamentally from cultivation from spores. When a mushroom releases spores, each spore represents a new genetic recombination—offspring of the parent but not genetically identical to it. If a wild Agarikon fruiting body is allowed to drop its spores and those spores are later cultivated, the resulting mycelium will be a different organism genetically, even if it belongs to the same species. Tissue culture, by contrast, bypasses sexual reproduction. The tissue taken from a single fruiting body contains living mycelium—the vegetative body of the fungus—that is a clone: a genetically exact copy of the original organism. When that tissue is grown in culture, all descendant mycelium remains genetically identical to the parent.
This distinction is critical for conservation. A wild Agarikon fruiting body with exceptional medicinal potency cannot be preserved by collecting its spores, because spores from that fruiting body will produce genetically different offspring. Only by cloning the mycelium itself can that unique genotype be immortalized in perpetuity.
What Makes This Technique Applicable to Endangered Species?
The cork borer and tissue culture method is non-destructive and scalable—two properties essential for conservation of endangered organisms. Taking a small sample from a wild fruiting body does not kill the organism and does not prevent it from continuing to produce spores and contribute to wild reproduction. In contrast, harvesting the entire fruiting body for commercial use, traditional medicine, or even research removes that organism from the ecosystem and eliminates its reproductive contribution. By using the cork borer technique, researchers can visit a wild Agarikon colony, take multiple small samples from different conks without harming any of them, and leave the ecosystem intact.
Moreover, the technique scales: the same approach that works for a single endangered fungus can be applied across multiple species and multiple populations. A mycologist can visit old-growth forests across different regions and climates, collect tissue from strains adapted to those specific environments, and preserve each one independently. Over time, a genetic library of a threatened species can be assembled without any impact on wild populations.
What Are the Limitations and Challenges?
Success is not guaranteed. Stamets estimates that only 2–3 fragments out of 10 plated will successfully establish mycelial growth and avoid contamination. Competitor organisms—faster-growing molds and bacteria—can overrun a plate within days if even tiny spores or cells are present. Maintaining strict sterility throughout multiple culturing steps requires skill, attention, and experience. Contamination can come from the original tissue (spores or bacteria already present inside the conk), the environment (airborne spores or dust), or the tools and media (if sterilization is incomplete). A single lapse in technique can result in loss of a strain that may never be accessible again in the wild.
Additionally, culturing Agarikon is slow. Petri dishes may take weeks to fully colonize. Test tubes take weeks to months. In the cold storage state, mycelium is dormant and not actively growing, so revival for propagation requires time and attention. For a mycologist managing 72 strains or more, maintaining backup cultures, monitoring for contamination, and periodically reviving strains to ensure their viability is a continuous labor.
What Is the Larger Goal of Strain Banking?
The ultimate aim is not simply to preserve Agarikon as a biological artifact, but to enable future research and restoration. As genomic and chemical analysis techniques improve, researchers will be able to extract more information from each strain—identifying novel compounds, understanding the genetic basis of medicinal potency, and potentially using genomic data to guide re-introduction efforts in wild forests. If a particular strain proves to have exceptional anti-cancer or immunomodulating properties, that strain's genetics can be sequenced and compared with wild populations to identify populations worth protecting. In a climate-changed future where old-growth forests face unprecedented pressure, the strain bank serves as a genetic library that can replenish wild populations and ensure that no unique lineage is lost to extinction.
Where to Go from Here
Those interested in applying this technique to other fungi should focus on mastering aseptic technique first. Cleanliness, proper sterilization, and careful handling are the foundation of all tissue culture work. For wild foragers and citizen scientists, the cork borer method is accessible without advanced equipment—a cork borer, sterile bags, and a cool place to transport samples are all that is required for field work. Laboratory culturing requires a pressure cooker for sterilization, petri dishes, nutrient agar, test tubes, a refrigerator, and basic tools (scalpels, forceps, cloth). For those working with endangered or threatened species, consult local regulations and obtain appropriate permits before collecting any wild material. Stamets's work with Agarikon, conducted in collaboration with Dr. Pamela Kryskow, demonstrates that even small-scale, careful collection efforts can accumulate into a substantial research resource over time—and that the preservation of mycodiversity is both scientifically and ethically important.
