Mushroom mycelium is a living organism. It grows by dividing cells. As with all living creatures, there is a limited number of cell divisions that can occur before the organism grows old, slows down, and then eventually dies. With fungi, we refer to this process of degeneration as senescence.
To avoid senescence, experienced mushroom growers store their cultures under refrigeration, which greatly slows down the process of cell division, prolonging the life of the organism. The process of making master culture slants and storing mycelium that is demonstrated here has proved to be capable of storing mushroom tissue for at least two years without further work. This is accomplished by placing a small piece of hardwood into each test tube along with the agar medium and mushroom mycelium.
The mushroom mycelium colonizes the nutrient soaked hardwood, and can then become dormant and last for at least 2 years. I have several cultures that have been in storage this way for nearly ten years and they are still viable. Each year, I take out a small piece of mycelium to test. If it grows well, it’s then used to inoculate grains to start the process of growing mushrooms. The original master culture slant is then placed back into refrigeration.
If you choose not to use wood in your culture slants, I'd suggest making transfers at least twice per year to avoid losing your cultures. When making transfers from culture slants, cut a small piece of mycelium and transfer it to a Petri dish. Allow it to grow out approximately 1 cm(unless contamination appears sooner), and then transfer from the leading edge of the growth to a new Petri dish. Once the mycelium on the second dish grows out 1cm, if no contamination has become evident, place a tiny piece of mycelium from the leading edge into a fresh test tube slant for further storage. The remaining mycelium on the Petri dish can then be used to inoculate grains for mushroom growing.
Enjoy the clip.
Marc R Keith