According to the different requirements for edible fungi production and cultivation on various comprehensive factors such as the seed production process, reproduction and expansion steps, isolation and inoculation methods, the strains are artificially divided into three levels:

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(1) First-level strains

Also called mother strains and test-tube strains (Figure 2-1), they refer to spores, fruiting body tissues, mushroom (ear) wood or matrix bacteria. The mycelium, spores and their culture substrate are separated and purified from silk and propagated on test tube culture medium. There are three sources: obtained through various breeding methods; directly isolated from the fruiting body itself (tissue and spores) or mushroom wood (earwood) (also known as the original mother species); packaged in test tubes or cultured imported from home and abroad. bacteria in the dish. Because most of the containers used to package primary bacterial strains are test tubes of different specifications, they are also known as "test tube strains". It is mainly used for the isolation, purification, tube transfer, expansion and preservation of bacterial strains. The number of original mother seeds is small. Some of the original mother seeds are used for preservation in test tubes, and the other part are transferred into tubes and expanded into mother seeds for production.

Figure 2-1 First-level strains

(2) Second-level strains

Also called original strains (Figure 2-2), consisting of first-level strains Breeded by species. Its culture medium is mainly made of natural materials and is a solid semi-synthetic culture medium formulated with an appropriate amount of soluble nutrients. This culture medium is closer to the production matrix. Therefore, secondary species can be directly used for production cultivation. However, due to the small number, the cost is too high if used for production. Only after breeding into third-level species can they meet the needs of production. For this reason, second-level species are also called transitional species, that is, from first-level species to third-level species. Transition, from a small amount to a large amount. During this transition process, in order to ensure the high purity of the third-level species, it is necessary to emphasize the use of high-pressure sterilization and other standardized operations for bacterial culture medium sterilization, just like the first-level species.

Figure 2-2 Second-level strains

(3) Third-level strains

Also called production strains and cultivated strains (Figure 2-3), In order to meet the needs of large-scale cultivation (production), it is a strain obtained by expanding the second-level bacterial strain. The culture medium is basically the same as or closer to the cultivation medium than the secondary species, and it is a strain directly used for cultivation. Since the third-level strain is the main product of the strain farm and participates in the circulation of goods, in order to facilitate transportation, avoid container damage, and also to reduce production costs, polypropylene plastic bags or vinyl bags are often used instead of strain bottles. In terms of quantity, one first-level species can produce 6 to 8 bottles of second-level species, and one bottle of second-level species can produce 20 to 40 bags of third-level species.

Figure 2-3 Third-level strains

The reproduction process of strains not only increases the number of strains, but also is the continuation and verification of the strain selection process. During the breeding and cultivation period, it is necessary to continuously retain the good and eliminate the bad. This is an important technology that strain producers need to master.