Obtaining A Culture
Methods of obtaining a culture are: tissue culture, spore germination, or purchase of culture from a culture collection.
Tissue cultures are the simplest way to obtain a mycelial culture. A tissue culture is essentially a clone of a mushroom. Clone is defined as an identical duplicate of an organism. The basic procedure is to sterilely remove a piece of the mushroom cap or stem, and place it on an agar plate. After a week to ten days, mycelium grows from the tissue and colonizes the agar. Great care should be taken to select a fruiting body of the highest quality, size, color, shape or any highly desired characteristic.
Mushroom spores are found on basidia lining the gills of the cap. To collect the spore, the cap is hung over sterile filter paper in a spore collecting chamber. Spore cultures differ genetically from tissue cultures. Cultures originating from spore germination are unpredictable. Spores germinate creating many different genetic combinations that are desirable when attempting to develop new strains, but undesirable when trying to maintain a specific strain. There is no way to predict if a culture's fruiting potential is similar to its parent other that to test many different lines obtained from spore germinations. Hundreds many be tested before obtaining a culture with good production potential.
Culture Validation Cropping Trials
There is no in-vitro test to determine a stock culture's validity. A series of cropping trials must be conducted on the mycelial stock culture to determine a culture line's value. Mushroom yield, size, color, cap shape and any other desired quality or growth factors are selected and then compared for each culture line.
Sub Culturing (agar to agar transfer)
Once a culture is obtained by whatever means, it needs to be maintained to preserve its viability. Agar to agar transfer (sub culturing) it the most popular culture maintenance method. Vegetative propagation of a mushroom culture is uncomplicated, but labor intensive. A small amount of mycelium from a mother culture is used to innoculate multiple fresh agar slants (these become the daughter cultures). The daughter cultures, after incubation at room temperature ~74F for 2 weeks. Are visibly screened for traits expressed in the mother culture. Then, one elected culture becomes the "new" mother culture. The new mother culture is stored in a refrigerator incubator at ~5C. After two months this culture is taken from refrigerator incubation and further transferred to freshly prepared agar slants repeating the cycle.