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96 CULTURING MUSHROOM MYCELIUM ON AGAR MEDIA
Figure 73. A laminar flow bench suitable for home
or small-scale commercial cultivation.
ing the sterile airstream. If the lids must be laid
down, they are positioned undersides up, upstream
of the operations area, so that
contaminants are not picked up off the table.
Always presume the air coming off the face of
the micron filter is cleaner than the work surface
in front of it.
Culture transfers that are fast, evenly repeated,
and in quick succession usually are the
most successful.The simplest acts dramatically
impact sterile technique. Merely breathing over
exposed petri dishes significantly affects contamination
levels. Singing, for instance, is
associated with a high rate of bacterial contamination.
One bewildered professor discovered
that her soliloquies in the laboratory—she sang
as the radio blared—were a direct cause of high
contamination rates. An alert student discovered
her digression from sterile technique upon
passing the door to her lab. This illustrates that
the cultivator's unconscious activities profoundly
influence the outcome of tissue culture
transfers. Every action in the laboratory has
significance.
Cloning Wild Specimens vs.
Cloning Cultivated Mushrooms
Many people ask "What is wrong with just
cloning a nice looking specimen from each crop
of cultivated mushrooms to get a new strain?"
Although morphological traits can be partially
selected for, senescence factors are soon encountered.
Generating mycelium in this fashion
is a fast-track to genetic demise, quickly leading
to loss of vigor and yield. By not returning
to stock cultures, to young cell lines, one has
gone furthest downstream one linear chain of
cells. Mushrooms, like every sexually reproducing
organism on this planet, can generate a
limited number of cell divisions before vitality
falters. Sectoring, slow growth, anemic mushroom
formation, malformation, orno mushroom
formation at all, are all classic symptoms of senescence.
Although senescence is a frequently
encountered phenomenon with cultivators, the
mechanism is poorly understood. (See Kuck et
al., 1985.)
In the competitive field of mycology, strains
are all-important.With the aforesaid precautions
and our present day technologies, strains can be
preserved for decades, probably centuries, allthe-while
kept within a few thousand cell
divisions from the original culture. Since we still
live in an era of relatively rich fungal diversity,
the time is now to preserve as many cell lines
from the wild as possible. As bio-diversity declines,
the gene pool contracts. I strongly believe
that the future health of the planet may well depend
upon the strains we preserve this century.
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