What to Do About Mushroom Spawn Degeneration? Causes and Countermeasures Explained

I. What Is "Mushroom Spawn Degeneration"

"Spawn degeneration" is the biggest concern for mushroom growers.

In microbiology, "spawn degeneration" (spawn decline) is defined as: during cultivation or preservation, due to spontaneous mutations, certain original superior production traits deteriorate and genetic markers are lost, and this phenomenon is called spawn decline. "Mushroom spawn degeneration" is a very abstract phenomenon that is hard to define specifically in words. We can think of it this way: in mushroom production, when the genetic traits of the spawn (mother culture) change, leading to a decline in yield and quality, this phenomenon is called "mushroom spawn degeneration." The decline in yield and quality is the final result of "mushroom spawn degeneration." To avoid "mushroom spawn degeneration," we must understand clearly what causes it and what its manifestations are.

II. Causes of "Mushroom Spawn Degeneration"

1. Cultivation environment

The growing environment for mushrooms includes: temperature, humidity, light, and oxygen. Among these, the environmental factor most likely to cause "mushroom spawn degeneration" is temperature, because temperature has the greatest impact on biological metabolism. When in an extremely unsuitable temperature environment, the genetic characteristics of the spawn change, losing the superior production traits it should have. During mother culture cultivation, preservation, and transport, exposure to high temperatures or low temperatures (such as below zero), can very easily cause "mushroom spawn degeneration."

2. Culture medium

A culture medium unsuitable for spawn growth will cause "mushroom spawn degeneration," including: the nutrient composition of the medium, pH value, medium that is too rich, medium that is too poor, or simply a medium unsuitable for its growth. Regarding mushroom mother culture media, existing theory and textbooks lag far behind actual production. So-called theories such as alternating poor and rich media are all applications of microbiological theory and concepts, and have no practical guiding significance in industrialized mushroom production.

3. Number of transfers

Too many transfers: from a microbiological theoretical basis, too many transfers can easily lead to "mushroom spawn degeneration." But in actual mushroom production, it should be: transfers using incorrect spawn preparation and cultivation methods easily cause "mushroom spawn degeneration," and the more transfers, the greater the possibility of causing "mushroom spawn degeneration."

4. Oidia, arthrospores, and conidia

For varieties that can produce oidia, arthrospores, and conidia during the mother culture mycelium stage, "mushroom spawn degeneration" easily occurs. Oidia and similar structures will germinate into mycelium when conditions are suitable, and this mycelium has no fruiting ability, or very poor fruiting ability. After continued transfers, they mix together with normal mycelium. As a whole, there may be no visible indication from the appearance of the mycelium, but ultimately it will affect the final yield and quality.

5. Spawn preservation

Mushroom production cannot be separated from spawn preservation. Improper preservation methods, excessively long preservation time, and preservation temperatures that are too high or too low can all potentially cause "mushroom spawn degeneration." Especially during preservation, if fruiting bodies appear on slant mother cultures, although the fruiting bodies will not grow very large, as long as a cap forms, spores may be discharged onto the slant, and when conditions are suitable they will germinate into mycelium, creating a situation where asexual reproduction and sexual reproduction are mixed together, causing "mushroom spawn degeneration."

III. What Are the Manifestations of "Mushroom Spawn Degeneration"

"Mushroom spawn degeneration" is most severe when manifested in a variety or a strain. There are many mushroom varieties, and the specific manifestations differ. If: mycelium grows slowly, tip growth is uneven, growth is sparse, more pigment is secreted -- in short, at the mother culture stage, if continuous, heritable abnormal manifestations appear, it is very likely that spawn degeneration has occurred.

The several manifestations of "mushroom spawn degeneration" described above are mostly not obvious. But if final yield and quality decline continuously, and the influence of the fruiting environment can be ruled out, then "mushroom spawn degeneration" should be considered. In severe cases, it shows during primordium formation and fruiting body differentiation, and an increase in deformed mushrooms is also one of the bases for judging "mushroom spawn degeneration."

"Mushroom spawn degeneration" does not happen in a short time, nor does it suddenly appear after a single transfer. Therefore, the manifestations of spawn degeneration come quietly and silently, which makes it even easier to overlook.

IV. How to Avoid Mushroom Spawn Degeneration

In response to the several causes of "mushroom spawn degeneration" described above, providing a suitable growing environment for spawn growth, a suitable culture medium, reducing the number of transfers as much as possible, reducing oidia, reducing arthrospores, reducing conidia, and doing a good job of spawn preservation can avoid "mushroom spawn degeneration" to the greatest extent possible.

In a word, carrying out spawn production according to formal and rigorous technical requirements is the fundamental method for avoiding "mushroom spawn degeneration." Once spawn degeneration occurs, the spawn should be replaced promptly.