(Kind of a side topic) Since you mentioned mycelium age, I would guess that genetic degradation happens similar to cannabis. Granted, it can take dozens of generations for clones of clones to degrade in cannabis, it seems to me that mycelium might age faster? I dunno. That would make sense if it wasn’t for the prevalence of PE strains that have been around for years. (I am not a genetic scientist by any stretch.)
Oof, love this topic. Yes, mycelium ages and accumulates mutations. The extent to which it happens is species-specific, and I think the number of times that the cells have multiplied is more important than absolute “time”. So, usually you notice a culture aging as you sub-culture it, meaning that you will grow the fruit and clone the fruiting body. Cloning the fruiting body allows you to preserve a strain, but after a few cycles of doing this the strain begins to degenerate. So, that’s why one might want to keep a master of the strain under storage. Eventually, even that master may degrade, and that’s when you need to breed again from spores. One can grow fruits directly from a mixed population of spores, but the results can be varied. A strain is isolated when one wants more consistent results.
As I said, this is species-specific. I think Lion’s Mane and oyster mushrooms can do lots of sub-cultures. Psilocybin mushrooms can also handle a few before showing malformed fruits and losing their spores.
But if you really want to get into the cool stuff of strain degeneration… Cordyceps militaris. This is a mushroom that is becoming very popular and it is famous for its strain degeneration and the necessity to breed it - which is not so easy - this is a mushroom meant to grow as an insect parasite. If you are into the details of what is actually happening as this mushrooms is sub-cultured, I recommend this paper.
Here is a very cool image of what sub-cultures look like form that paper:
Working with this mushroom is a beautiful exercise of sourcing. Because of its popularity, many vendors are selling it now… But they will give you a strain that fruits like Z4/Z5. If you want a strain to fruit like first-generation fruiters you need someone who either collects spores from the wild, is a breeder, or knows how to source them and store them well. A youtuber I like watching (Fresh From The Farm Fungi) made a series of experiments trying to breed this fungus. He is very experienced, and you can see that even for him it’s quite a challenge: www.youtube.com/watch?v=NRm859-mjhM
But… yeah, this is probably more than you wanted to know about ageing in mycelium… Sometimes when I’m excited about a topic I talk a lot 😂