There are large varieties of bacteria, among them, common bacterias are bacillus, Pseudomonas fluorescence and Erwina sppP.
1. The symptom of harm: After getting contaminated by bacterias on mother strain, the surface of substrate presents damp and holds evident colony. Some even send out a stink and affect the normal growth or cause bad growth on spawns of King oyster mushroom. During the cultivation process of compost, it becomes stink and rotten after getting contaminated by higher amounts of bacteria, especially in kernel strain, thick bacteria liquid appears and stink smell sends out on that occasion.
2. The conditions of attack: There are large varieties of bacteria which contaminate substrate and compost, the sources are extremely wide. For instance, bacteria floats in the air, all kinds of organic matters carry with bacteria and they even can be found in water. During the inoculation process, halfway sterilization in inoculation room and inoculation box, lax adherence on aseptic operation procedures or original bacteria from strain may cause bacterial contamination. In terms of compost or substrate, when the PH Value presents neutral or faintly alkaline reaction and partial high on water content, it will be fit for the growth of bacterias. In terms of temperature, high temperature or slight higher temperature on material are fit for the growth of bacteria.
3. Control method:
A. Demands on raw materials of compost: Straw, cottonseed hull, corncob and other materials should be fresh and free from mould. Moldy compost should be handled by compost fermentation on high temperature. What’s more, clean well water or river water should be used to mix materials, use 50% of carbendazim which weights 0.1% on dry material or 0.1% of thiophanate methyl to mix materials. The last important thing is that the water content of compost and the temperature of the cultivation room shouldn’t be too high.
B. When expanding mother strain, you could combine with a small amount of streptomycin or other antibiotics on sterilized substrate in an attempt to prevent the growth of bacteria and guarantee no bacterials in strain. But when dropping streptomycin to test tube, aseptic operation should be applied to prevent that bacterial contaminate is stopped while mold contamination is brought about. What’s more, it is suitable to keep the concentration of antibiotic at 100-200 of international unit in per ml.
3. During the process tube-conversion on strain or expanding cultivation, you could firstly guarantee that the sterilization of substrate is thorough, then they should strictly adhere to aseptic operation during the whole process.
4. In strain production, mother strain used for expanding inoculation or original strain should be free from bacterial contamination. When choosing wheat as strain, firstly ensure that they are free from Gibberella zeae or breakage. Too high water content also should be avoided and strict sterilization should be conducted as well.
5. The PH Value of Potato Sucrose Agar Substrate should be adjusted to weak acidity so as to inhibit the growth of bacteria.
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