GROWING GOURMET - Anto2ni.it

122 EVALUATING A MUSHROOM STRAIN
gering fruiting, the mycelium remains in stasis,
what cultivators term "over-vegetation."
Volvariella volvacea, the Paddy Straw Mushroom,
will not produce below 75° F. (24° C.) and
in fact, most strains of this species die if temperatures
drop below 45°F. (7.2° C.). Pleurotus
pulinonarius, a rapidly growing Oyster species,
thrives between 75-85°F. (24-29°C.) and is not
prevented from fruiting until temperatures drop
below 45° F. (7° C.). With most temperaturetolerant
strains, higher temperatures cause the
mushrooms to develop more quickly. Another
example is Pleurotus citrinopileatus, the
Golden Oyster, which fruits when temperatures
exceed 65°F. (18° C.).
10. Number and distribution of primordial
sites For every cultivator, the time before
and during primordia formation is one of high
anxiety, expectation and hope. The change-over
from vegetative colonization to this earliest period
of mushroom formation is perhaps the
most critical period in the mushroom life cycle.
With proper environmental stimulation, the cultivator
aids the mushroom organism in its
attempt to generate abundant numbers of primordia.
Aside from the influences of the
environment and the host substrate, a strain's
ability to produce primordia is a genetically
determined trait. Ideally, a good strain is one
that produces a population of numerous, evenly
distributed primordia within a short time frame.
11. Site-specific response to low carbon
dioxide levels As the mycelium digests a substrate,
massive amounts of carbon dioxide are
produced, stimulating mycelial growth but preventing
mushroom formation.The pronounced
reaction of mycelium to generate primordia in
response to lowering carbon dioxide gives the
cultivator a powerful tool in scheduling
fruitings. Strains vary in their degree of sensitivity
to fluctuations in carbon dioxide.
Mushroom cultivators who grow Oyster mushrooms
in plastic columns or bags desire strains
that produce primordia exactly where holes
have been punched. The holes in the plastic
become the ports for the exodus of carbon dioxide.
At these sites, the mycelium senses the
availability of oxygen, and forms primordia.
This response is very much analogous to the
mushroom mycelium coming to the surface of
soil or wood, away from the CO2 rich environment
from within, to the oxygenated
atmosphere of the outdoors, where a mushroom
can safely propel spores into the wind currents
for dispersal to distant ecological niches. With
strains super-sensitive to carbon dioxide levels,
the cultivator can take advantage of this sitespecific
response for controlled cropping,
greatly facilitating the harvest.
12. Number of primordia forming vs.
those maturing to an edible size. Some
strains form abundant primordia; others seem
impotent Those which produce numerous
pri-mordia can be further evaluated by the
percentage of those forming compared to those
developing to a harvestable stage. Ideally, 90%
of the primordia mature. Poor strains can be
described as those which produce primordial
populations where 50% or more fail to grow to
maturity under ideal conditions. Aborted primordia
become sites of contamination by
molds, bacteria and even flies.
13. Number of viable primordia survivingfor
2nd and 3rd flushes Some strains of
Oyster and Button mushrooms, especially coldweather
varieties, form the majority of
primordia during the first initiation strategy.
Many primordia lay dormant, yet viable, for
weeks, before development.After the first flush
of mushrooms matures and is harvested, the
resting primordia develop for the second and
subsequent flushes.
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