Culture Sketch: Smoky Mountain Reishi

A Sample of Smoky Mnt. Reishi grown from the cloned culture.

In the summer of 2012, an incredible mushroom was found in Sevierville, TN. An old persimmon tree had been cut down and paved over, and rising from that stump, punching straight through the pavement, even, was a massive reishi mushroom. Called Ling Zhi in Chinese, “the mushroom of immortality,” reishi has a long history as a medicinal mushroom. Andrew was approached by Hugh Brewer, of Brewer’s Mushrooms, with a sample of this amazing mushroom, and it was agreed that Andrew would clone it for Hugh, and both would keep a copy of the culture to use.

Andrew sanitizing his hands in the lab

Cloning animals is a very challenging process, but things are very different with mushrooms. Anyone can clone a mushroom, and, with the right equipment, the process is very simple. Andrew started with nothing more than a simple plastic tote with holes cut in the sides for his hands. He would sterilize the box with bleach and use sterile procedures to keep the cultures clean. Now he has a HEPA filter blowing pure air over his work station in the lab, but the concept is the same: provide a sterile environment to work in.

First growth on agar

Clean growth

Hugh brought the reishi mushroom to Andrew at his lab, which at that time was in the old General Store in Old Town Jefferson City. To clone the mushroom, he cut a small chunk out of it and placed it in a petri dish with malt extract agar in it. The secret here, is that the tissue must be as clean as possible, so Andrew always tears a large piece open and cuts from the inside tissue. A common mistake is to cut from the outside, which tends to bring microbes from the outside surface of the mushroom through on the scalpel, which will increase contaminates.

Preparing to transfer to a new dish

Once you’ve got the petri dish prepared, you’ll have to wait for the culture to grow out. This part is important because you’ve got to make sure the culture is viable, and free of contaminants. If it grows out clean, it is ready to use. It’s more likely, however, that it will have some contamination on it. If the culture is contaminated, you’ll need to clean the culture by cutting the cleanest part out and placing it in a new petri dish with the agar mix, allow it to grow in again, and repeat until the culture is clean.

Once Andrew got a clean culture, a sample of that reishi was sent to the North American Ganoderma Society for testing. This reishi was unique, and for a while it seemed that Hugh had found a whole new species of mushroom. Those were exciting times, because three other samples were found of the same species, all from the same region as the original sample. The name Ganoderma Tennessee was discussed as it’s official classification.

Our excitement was dimmed a bit in the end when further testing showed that the sample Andrew sent matched another rare specimen: Ganoderma Martinique. This mushroom had previously only been found on the island of Martinique, which is east of Puerto Rico. One of the amazing things about mushrooms is how far they can send their spores: this mushroom seems to have traveled all the way across the ocean and then naturalized in the Smoky Mountains. While we didn’t, in the end, discover a new species, it was an exciting moment in the history of Mossy Creek Mushrooms.

Smoky Mountain Reishi

The Smoky Mountain Reishi has become known for its mild taste, less bitter than most, but its growth is very slow. When a mushroom is cloned, all the original properties of the mushroom are maintained, but hundreds or even millions of mushrooms can be grown out that are genetically identical. In the mushroom world, we keep these “strains” because we know exactly what to expect when growing our mushrooms, but what about if we wanted to develop new attributes? In that case, we would breed a new strain by growing from spores.

Oyster mushroom spore print

Now, if Andrew had wanted to breed a new strain; instead of cloning the one he had, he would have started by taking a spore print, instead of cutting off a chunk of the original mushroom. To do so, he would put a clean surface under the mushroom and let the spores fall onto it, while keeping the environment as clean as possible to cut down on contamination from other spores, like mold. Once enough spores are collected they are shaken into a petri dish with the agar in it. If two strains are to be bred together, then spores from each would be placed together on the dish. Once they’ve grown in, the new strains must be isolated by transferring them to a new dish. 

Mushroom mycelium growing into grain

Culture slants preserve mushroom cultures for years, allowing a grower to keep a strain alive in deep storage

This part of the process can be quite lengthy because the culture may take a few days to a week for each plate to grow in, and the process usually must be repeated several times before the culture is pure and ready to be used to make grain spawn, which we will discuss in the next post.

Whether bred or cloned, Andrew usually uses his cultures as soon as they are ready, but, if needed, there are a few methods that can be used to preserve a culture. Keeping it refrigerated will keep it usable for six months to a year. A culture slant can be used for longer storage. It is simple to prepare: a test tube with the agar mix in it kept at an angle with a small piece of mushroom tissue placed inside. It is sealed, and the varied depth of the agar mix and the sealing slow the growth of the mycelium so it will last up to seven years. High-end culture banks and spawn laboratories use liquid nitrogen to deep freeze cultures. It is hard for a small operation to use, but can keep your culture preserved indefinitely.

While the process is fairly simple, especially after you’ve been doing it repeatedly for a long time, beginning any new project can be daunting. If you enjoyed learning about the process, or there’s anything you’d like us to clarify before you get started on your own cultures, feel free to post a comment, and join the discussion.