Xianggu(Lentinula edodes) is the second most important
cultivated mushroom in the world and a well establishes industry in Asia, especially in
China and Japan.
Historical records have shown that xianggu cultivation in China could be dated back to
more than 1000 years ago. Xianggu was first cultivated semi-artificially on old
trees in mountains by natural inoculation of spores from neighbouring infected logs, the
wood-cutting technique for Xianggu cultivation prevailingly used in the mountainous areas
of Zhejiang Province was described in Wang Cheng'sˇ¶Agriculture Bookˇ·published in 1313.
Beginning from the 30's of this
century when the cultivation method of Xianggu was newly introduced from Japan to
Fujian,Zhejiang Province of China, much interest was aroused to the pure culture technique
and method of preparing culture substrate for Xianggu Mushroom.
A series of performed techniques promoted
expansion of the cultivation of the variable mushroom and the reform of traditional method
of cutting wood processes in the mountainous areas.
There are two main cultivation methods of
Xianggu, namely:Bed-log cultivation and plastic bag cultivation.
BED-LOG CULTIVATION
There are six key
cultivation phases:
1.Spawn and Spawn-making:obtaining viable
inoculum in pure culture and storing it in cool low temperature until use;
2.Preparing logs for cultivation;
3.Inoculation; 4.Laying the logs to favour fungal growth; 5.Raising to favour fruiting;
6.Harvesting and storing the crop.
1.Spawn and spawn-making
Before cultivation
growers must prepare viable Xianggu spawn of a good strain in pure culture, free of
contamination.
Xianggu spawn in
China is usually grown on sawdust-bran media and is usually supplied in sealed glass
bottles or plastic bags, occasionally it is grown on small peglike or rod-shaped pieces of
wood, 1-1.5cm in diameter by 1.5-2cm length.
Mixture of sawdust
and rice bran are used for the media of spawn. It is autoclaved and inoculated with
mycelia of Lentinula edodes and keep in incubators at a temperature between 20-28ºC.
The spawn should be moist white and appear rather fuzzy. Bacteria and weed molds are keep
out by not damaging or opening the spawn bottles or bags until use of the entire contents.
Storage for a month or more should be in a cool location(4-10ºC), away from direct
sunlight.
2.Felling trees and preparing logs for
inoculation
(1)Suitable trees
For Xianggu
cultivation,the suitable trees are Castanopsis hystrix, Castanea mongipetiolata, Castanea
mollissima, Cyclobalanopsis glauca, Fagus longipetiolata, Quercus acutissima, Quercus
serrata, Quercus variabilis, Betula tauschii,Carpinus laxiflora, Liquidambar formosana,
Altingia chinensis, Altingia gracilipes, Elaeocarpus sylvestris and so on.
(2)Felling
season
From late
autumn to early spring, trees should be felled when about one third of the leaves turn red
in autumn. At this time, the sugar content of the sap is high, which is beneficial to
Xianggu mycelial growth, but low temperature retard the growth of competitive weed fungi.
The log barks tend to be better when the trees are cut while leafless and and especially,
when they are cut in the late autumn ,bark supports mycelial growth and Xianggu fruit body
production by maintaining the log water content, by insulating preventing from rapid
changes in growth of competitive fungi at the log surface. Barks also help to stimulate
fruiting. Therefore bark damaging (the bark on the logs)should be avoided.
The felled trees
should be kept on well-drained ground in a location with good air circulation and
unsheltered from small rain fall, which is necessary to keep them moist. Prior to
inoculation, the trunk and large branches are cut into logs. In Fujian, Jiangxi,
Guangdong, Hubei provinces, some growers prefer to white-wash the bare wood on the ends of
the logs with lime water, that will inhibit entry of competitive fungi. The optimal log
size is 5-15(20)cm in diameter and 0.8-1 meter long. The thicker branches are also used.
3.Inoculation
Xianggu spawn
should be introduced into logs no sooner than 2 to 3 weeks after the tree is felled. If it
is introduced earlier, the spawn probably will not survive. The drying period allows time
for the tree cells to die before inoculation.
Because the logs
are not sterile, it is very important to distribute the spawn into many place spots of the
surface layer spaced evenly the log service.
Holes are drilled
into the log in rows lengthwise to the logs. Holes in each row are spaced roughly 20-40cm
apart. Rows are 5-10cm apart. Usually 10-30 holes of spawn are required per log. The holes
should be filled with sawdust spawn.
After inoculation
the surface of the log where the spawn was introduced should be covered with a piece of
bark or lightly painted with hot paraffin to seal in moisture and to disinfect the
surface. Inoculation should be done in a shaded area to avoid direct exposure of the the
spawn to sunlight.
4.Laying the logs
After inoculation,
the logs are placed in a position favorable for the development of the mycelium. Logs are
laid side by side propped up at a slant in a well-drained shaded area with single logs
placed crosswise between rows.
The piles of bed
logs are covered with twigs. Straw mat or other materials in order to keep out the
extremely dry air(to prevent from excessive heating due to direct exposure of sunlight and
to favour moisture retention while still allowing aequate ventilation and wetting during
rainfall.
Prelaying continues
until the rainy season and process of laying is now considered complete. If
conditions are excessively hot and moist the bark should be removed to promote surface
drying to encourage uniform water distribution, which promotes uniform growth, the logs
should be turned (reverse the ends) every 2 to 4 months.
Optimum temperature
in the laying yard is between 15 and 28ˇăC and relative humidity 80 to 85% is necessary in
practice, most failure in Xianggu cultivation in Fujian, Jiangxi, Guangdong, Hubei
provinces have been traced to indirect condition in the laying yard that favour
competition from weed fungi.
5.Raising
After the mycelia of
Xianggu has developed into the log as may happens any time after 6-8 months, one year or a
year and a half after inoculation, depending on species of tree, spawn, climate and laying
conditions, the logs are now ready to fruit, which require abundant moisture, sufficient
air movement and shaded exposure to light. Fruiting is usually constantly high relative
humidity of at least 80 to 85% are optimal.
To provide these
conditions and to facilitate harvesting, the logs should be uncovered and stacked on well
drained shaded ground. Each log is separated by the width of another log placed on the
opposite of the board.
Fruiting occurs primarily
in the wet, cool season-spring and autumn, once Xianggu begins to fruit on a log, it
generally continues to do so during spring and autumn for an additional 3-years.
If a summer is
particularly dry, the logs may be too dry to support autumn fruiting. For fruiting, log
moisture content should be over 40%,the higher, the better. For increase water content,
overhead sprinklers can be soaked in a stream or tub of water for 1 to 3 days. In large
scale production, prior to the fruiting, logs are usually kept drier than normal, and then
soaked in cool water(13-20ˇăC) to stimulate fruiting, within a week of being soaked, logs
become dehydrated usually produce bumper crops.
PLASTIC BAG CULTIVATION
OF
XIANGGU WITH SAWDUST MEDIA
In recent years,
Xianggu production has been advanced steadily, in many provinces of China mushroom growing
has sprung up as spring bamboo shoots burst out of the ground after a heavy rain and
various Xianggu growing techniques are blooming luxuriantly as hilly flowers everywhere.
According to the
statistics of The Edible Mushroom Association of China(1991), the total annual production
of Xianggu in China is around 30 thousand tons (dry mushroom).
A new method of Xianggu
growing was developed in Fujian, Zhejiang Province, several years ago. It is called
"the plastic bag cultivation" or "artificial bed-log cultivation".
In China, Xianggu is commonly
grown once a year from late autumn to spring, although the dates may vary slightly from
year to year.
The substrate for growing
Xianggu in plastic bags are sawdust of suitable broad-leaved trees with 20-25% rice bran
or wheat pollard to enrich the nutrient and sometimes calcium carbonate is added to adjust
the pH value of the substrate.
Dried sawdust is mixed
with rice bran or wheat pollard at a proper ratio and is adjusted to a measurable water
content(62-68%). The mixed sawdusts are packed into a plastic bag by hand or by bag
filling machine and pressured to form a cylindrical block. They are also called artificial
bed logs. Two ends of bags then tied with cotton strand and the free parts of two ends are
fused by heating. After filling, they are sterilized in an autoclave at 121-123ˇăC for 1-2
hours or in a special steaming room at 97-103ˇăC for 6 to 8 hours. Over-sterilization
causes extreme browning destroying nutrients and producing toxic compounds which slow the
spawn running. After cooling, bags are inoculated.
When inoculation, sawdust
grown spawn is used, the holes should be completely filled with spawn. Growers usually use
special tools(like injection auger) for making 4-6 holes on each side of these growing
bags, each hole is about 1cm in diameter and 0.5-1.2cm in depth. After the hole is
chiseled it is then covered with a 3 x 3cm white rubberized fabric to prevent the
evaporation of moisture and spawn falling. After inoculation, the bags are transferred to
a growing house, maintained at 23-25(-28)ˇăC.
Due to the soft texture
of the plastic bag and the medium it is necessary to take special care when moving the
bags.
After 60-80 days Xianggu
mycelium is fully grown, the bags are then transferred to the cropping house. The bags are
arranged on the growing frames, or to the "Sheltered Yard", and stripped off for
cropping.
A shelter frame is
mounted in the rice field, where several ridge beds, at a width of 1m and random length
are built. On both sides of the bed two pieces of log bamboo or wooden stick aretied or
nailed to the short sticks. Several short sticks are crossed on the long sticks, spacing
from each other at a width of stripped cylindrical sawdust block. Over each ridge bed
slices (sheets) of bamboo are arched into the earth, covered with a plastic film to
maintain suitable moisture.
Both the
temperature and moisture conditions of the cropping yard are very important. The optimum
temperature for forming fruit bodies is between 10-20ˇăC. The humidity of cropping yard
can be adjusted by spraying water on the cylindrical sawdust block to maintain 85%
relative humidity. Under these conditions, the surface of cylindrical sawdust block
gradually return white and then brewing.
Cylindrical sawdust
block have a short growing cycle 7-12 weeks to the first break and the biological
efficiency is up to 100%.
(References omitted)
