Analysis of the Concept of Disease- and Pest-Free Substitute-Material Shiitake and New Cultivation Techniques
The large-cup mushroom, also known as pig-stomach mushroom, has fruiting bodies that grow in clusters, cup-shaped or shallow funnel-shaped, pale yellow, with thick flesh and a thick stalk, crisp and tender and delicious, and rich in nutrients. Under natural conditions, the fruiting bodies appear from May to October, and it has the characteristics of both wood-rotting and soil-borne growth. Its cultivation essentials are briefly introduced as follows: 1. Seasonal arrangement: large-cup mushroom fruiting...
I. The Concept of Disease- and Pest-Free Substitute-Material ShiitakeThe concept of disease- and pest-free substitute-material shiitake mainly includes three aspects: (A) no competing miscellaneous microbes in the culture material, (B) no pest invasion, and (C) no physiological diseases. Its specific technical requirements are:
a. The sterile environment inside the tube bag before inoculation, or under normal temperature and oxygen-rich conditions, miscellaneous microbes (such as yeast) are in a relatively weak position.
b. The sterile state of the spawn blocks and the inoculation process.
c. The mycelium is in a relatively dominant state during the spawn-running process.
d. No erosion by mycophagous pests or infection carried by insect bodies.
e. Unobstructed development of the fruiting bodies. Under conventional mushroom-making conditions, only indicator A can possibly be achieved at a large energy cost (the culture substrate being sterilized at 97-100 degC for 10-12 hours), because while the plastic tube bag film isolates diseases and pests, it creates obstacles in the following two aspects.
II. Problems Existing in Disease- and Pest-Free Management
1. Because the mycelium must breathe, this causes an insufficient O2 concentration and a rise in CO2 concentration. At present, the domestic solution mainly relies on piercing holes to increase oxygen. While this method consumes a great deal of manpower, it also provides convenience for insect invasion, especially by Diptera insects, and under improper management it aggravates physiological diseases during the spawn-running process (see my humble work "Occurrence and Control of Physiological Diseases of Substitute-Material Shiitake," Chinese Edible Fungi, Issue 2, 2000; the occurrence of diseases and pests in the vegetative growth stage of edible fungi is all related to this).
2. Obstacles to fruiting body development increase the proportion of deformed mushrooms. In the craft of producing flower shiitake, in order to increase the difference in growth speed between the inner and outer surfaces of the cap, the isolation effect of the tube bag is generally used to create a humidity difference between the inside and outside of the film, achieving the goal of cracking into patterns. To solve the fruiting obstacle caused by the bag film, the domestic practice generally adopts the method of cutting openings to induce fruiting. If the timing of the cutting is not well controlled, it often causes an increase in the proportion of deformed mushrooms.
III. Introduction to Several New Cultivation Processes
1. New Sterilization Process
In production, the sterilization currently used is all normal-pressure (a few high-pressure) high-temperature sterilization. This physical sterilization method is built on the basis of energy consumption and time consumption, and has very strict requirements for heating equipment and the heating process. With technological progress, a more convenient sterilization method - normal-temperature chemical sterilization technology - is being developed. The intermediate-temperature sterilization technology between the two is becoming increasingly perfected, and its total application in production has exceeded 30,000 tons of culture material. The core technology of this sterilization method is to use a temperature of 60-80 degC to kill fungi that cannot tolerate high temperatures (such as green mold, yeast, etc.), and to use selective chemical agents and a certain temperature to kill fungi that tolerate higher temperatures (such as Aspergillus flavus). The reason heating to a moderate temperature (generally 60-80 degC) is needed is that at this temperature, low-temperature-type fungi (many of which are drug-resistant types) have already died, and at the same time the activity of the agents is enhanced at this temperature while the drug resistance of high-temperature fungal strains is weakened. As for normal-temperature sterilization, it is still not easy at present to find an acceptable meeting point in terms of selective sterilization, agent cost and residues.
It should be pointed out that the agents for chemical sterilization must possess several characteristics: a short residual effect period, strong selectivity, and residues not exceeding standards. Through many years of research and promotion, the intermediate-temperature sterilizing agent developed by the Qingyuan County Research Center has already been widely applied in the production field.
2. Application of New Breathable Tube Bags
The combination of new breathable tube bags with new sealing technology at the inoculation opening keeps the shiitake culture substrate in an oxygen-rich, miscellaneous-microbe-free state. The core of this technology lies in attaching a bacteria-filtering breathable film onto the membrane. According to my testing, the application of this kind of tube bag can isolate diseases and pests while fully satisfying the oxygen demand and CO2 discharge of shiitake mycelium. At 28 degC, the spawn-running speed is increased by % compared with the conventional method, the first-flush mushrooms appear about days earlier, and the total yield is increased by %. The recovery of losses from diseases and pests is difficult to measure because of inconsistencies in the environment and conventional mushroom-making levels, but under large-scale production conditions, theoretical analysis reaches more than 10%.
3. Culture Material Bag-Removal Water-Retention Technology
The key point of this technology lies in creating a layer of film on the shiitake mushroom sticks with the following functions: 1. Retain moisture; 2. Low tension to satisfy natural fruiting; 3. No toxic side effects on the human body or the mushroom body; 4. Low cost; 5. Easy to operate.
A new type of water-retaining agent, after being brushed onto bag-removed mushroom sticks, condenses into a water-retaining film layer, and this film layer can satisfy the above five requirements. Experiments show that after adopting this technology, deformed mushrooms are greatly reduced, the commercial value of shiitake is greatly improved, and at the same time surface green mold is effectively suppressed.
The Qingyuan County Research Center has made unremitting efforts on this project, and there have been lessons from failures and successful models; the widespread application of this technology in flower shiitake production is not far off.