If you wish to keep certain cultures of mushrooms for a prolonged time, it is recommend to do so by using the so called slants. These are test tubes filled with agar for mycelium to grow.
The slants can be sterilized with the agar extract inside. If you let the slants cool down after sterilization it’s wise to set them down. This gives the mycelium a bigger surface to grow in. After it’s cooled down you can inoculate the slant with for instance an isolated piece of mycelium from a single strain. When the mycelium gives signs of growth on the agar you can place the slants in the refrigerator (2 - 4 degrees C.).