What methods are there for identifying the quality of mushroom spawn stock?

I. Button mushroom. The mycelium is greyish white, slightly bluish, in the form of fine down, with the appressed mycelium evenly distributed top to bottom, no fan-shaped variation, no yellowish-white mycelial skin, and it has the characteristic mushroom aroma. If the mycelium in the substrate appears thin and shallow or in strands, the mycelium is pale yellow, shrunken or invisible, and the contents are pasty, this indicates excessive moisture or aged spawn; if the mycelium in the upper part of the substrate is dried and shrunken while the mycelium in the lower part still grows fairly well, this is caused by the substrate being too dry and the incubation temperature too high; a mycelial mat that is too thick on the upper part of the bottle indicates aged spawn or spawn with poor production performance; if white or pale yellow clumps appear in the bottle, or colonies of green, yellow, black or orange-red moulds and insect pests appear, all such spawn should be discarded.

II. Shiitake. Superior spawn has snow-white cottony mycelium, even growth, a distinctive aroma, no thick mycelial mat, easy formation of primordia, and resistance to diseases and insect pests. If the mycelium in the bottle is sparse and sawdust particles are visible, the incubation time is insufficient or the substrate is low in nitrogen sources; if the mycelium in the bottle has detached and shrunken and the mycelial mat has turned brown, the spawn is too old and should be used as soon as possible.

III. Oyster mushroom. The mycelium is dense, snow-white, thick and cottony, with a tendency to climb the bottle walls. If the mycelium is sparse or in strands, the substrate is too wet; if the mycelium grows slowly or does not grow downward, the substrate is too dry; if a large number of primordia appear inside the bottle or bag, the spawn age is too old; if the mycelium detaches from the walls and shrinks and yellow exudate accumulates at the base, the spawn is old; mould patches, antagonism lines and wet spots on the surface or bottle walls all indicate contaminated spawn.

IV. Wood ear. Snow-white, thick and vigorous mycelium that grows quickly, neatly and evenly indicates spawn with good traits; after a period of incubation, chrysanthemum-shaped gelatinous primordia appearing on the bottle walls, brown or dark brown, are a normal phenomenon. If the mycelium is sparse and substrate particles are visible, the reasons are similar to those for shiitake spawn; primordia appearing before the mycelium has filled the bottle indicate excessive physiological maturity or too many transfers. Pale yellow exudate at the base indicates over-aged spawn; if the mycelium grows only in one corner and no longer spreads, this is related to the moisture of the substrate.

V. Silver ear. When the ratio of silver ear mycelium to Hypoxylon mycelium is appropriate, a "white down ball" or gelatinous fruit body base forms on the substrate, the Hypoxylon mycelium in the bottle grows robustly and evenly and can produce black patches, and later distributes in strands beneath the fruit body base with no other foreign patches, while the silver ear mycelium penetrates deep into the substrate and is fairly thick beneath the fruit body base with vigorous white down balls and a large fruit body base, the spawn is superior. If the white down ball is rather small and readily gelatinises, the spawn has aged; if the Hypoxylon mycelium is sparse and does not penetrate deep into the substrate, and the fruit body appears as a gelatinous mass or gelatinous spines that do not open into flakes, the substrate is too wet; if the surface mycelium fades, the fruit body base turns red, and reddish-brown exudate is present, this is related to mite contamination; if a very thin mycelial film covers the substrate surface while silver ear primordia are still present below, the spawn is not pure.

VI. Enoki mushroom. Snow-white, thick mycelium or a fine powdery appearance, strong vitality, and the later appearance of small fruit bodies in clusters on the substrate indicate superior spawn. If the mycelium cannot grow deep downward and there is a distinct boundary, this is related to the substrate being too wet; sparse mycelium may be related to insufficient nitrogen sources in the substrate or declining spawn vitality; if fruit bodies appear on the bottle walls and the stipes extend out, this indicates the substrate has dried and shrunk and the mycelium has aged; if the contents of the bottle become slimy, this is bacterial contamination.

VII. Lion's mane. Snow-white, thick mycelium that grows fast and is evenly distributed top to bottom, and that readily forms plump, thick-fleshed fruit bodies on the substrate surface, indicates superior spawn. If the sawdust substrate turns pale yellow and the mycelium grows weakly, this is related to insufficient organic nitrogen or a relatively short incubation time; if primordia appear before the mycelium has run through half the substrate, this is related to continuous transfers; sparse, slender and unevenly distributed mycelium that is easily infected by foreign microbes is a sign of declining vitality; if the substrate shrinks and the bottom of the bottle fills with yellow slime, the spawn is aged.