Notes on Rehydration for Edible Mushrooms and Four Methods for Assessing Spawn Quality

I. Identification by Direct Visual Observation

In terms of appearance, if the mycelium of the spawn is thick and white, robust, and elastic, its vitality is strong; if the mycelium of the spawn is shrunken, dry and lacking in color, or if the mycelium has autolyzed and produced a large amount of reddish-brown liquid, its viability has already weakened and it should no longer be used; if wood-block spawn remains hard and solid, it is spawn with strong viability, but if the wood blocks become softened and loose, it has already aged and is not suitable for use.

II. Identification by Culture Observation

For spawn that has been isolated, selected and bred, or introduced, observe through culturing the adaptive characteristics of the mycelium with respect to dryness, moisture and temperature. For example, culture the mycelium under relatively dry, relatively moist, and moderately dry-and-moist conditions. If the mycelium grows well under the first two conditions but grows best under the moderately dry-and-moist condition, this indicates that it is good spawn.

III. Identification by Liquid Culture

Prepare a 2% sugar water solution and sterilize it by routine methods. Pick out a spawn block the size of a soybean and place it into 100 ml of the above solution. Culture it at 25—28°C for 3—7 days. If bubbles appear on the liquid surface, a film forms, and turbidity occurs, this indicates that the spawn itself contains contaminant microorganisms; if the spawn block sinks, or only produces a very thin mycelial layer after a long delay, this indicates that the spawn has weak viability; if the mycelium grows quickly around the edges of the liquid surface and is thick, white and cotton-like, this indicates that the spawn has strong vitality.

IV. Identification by Sawdust Bottle Culture and by Cycle Yield Assessment

The method for bottle culture identification is similar to that for cultivation. Fill the sawdust culture material somewhat loosely, increase the moisture appropriately, inoculate the spawn to be assessed into the culture medium, keep good records, and culture at a constant temperature of 26°C for 15 days. Then lower the temperature to 15—20°C, provide good scattered-light conditions, and culture for about another half month. Primordia of fruiting bodies and a small number of fruiting bodies will then appear on the bottle wall and the surface of the material. If no contaminant microorganisms or abnormal phenomena are found, then inoculate the spawn onto wood segments and carry out cycle yield assessment. If the fruiting bodies grow vigorously, with high yield and good quality, possess the characteristics of a fine variety, and no contaminant microorganisms are mixed in, this indicates that the spawn is reliable and can be preserved and put into large-scale production.