The spores of the species I have dealt with are not destroyed by dehydrating. But I expect that they may be destroyed by freeze-drying... Give it a try. You'll know in a few days.
The process of going from non-sterile to sterile involves a process called "culture plating"... Basically it involves diluting a culture enough times to separate the mycelia from the contaminates. Anti-biotics of one type or another can also be used... One of my favorites for mushroom culture is hydrogen peroxide. Since many species of mushrooms make peroxide as a natural anti-biotic, they are not harmed by it.
As a subsistence farmer, I prefer to do my mushroom cultivation in non-sterile conditions.
Interesting question Ken,
I thought along these lines when I was getting into it.
Spores are everywhere. Imagine the air flowing full of spores. Mushrooms when mature will emit spores. Their goal is to find a substrate. The odds are infinitesimally low. That's why they make so many spores. Some spores that are dried can be made into spawn. The odds are very , very low if you are not very very experienced.
People will take a fresh mushroom, with a small portion,usually from inside the mushroom with no contamination. Then they put it into increasingly large and usually different substrates, trying very hard to avoid all contamination. It's a fairly complicated process, but as Joseph mentions, there are less complicated versions with limited types of species if you aren't depending on making a living from the process.
Thanks! I'm not sure if I'll try it or not. I've already got two kinds of morels planted and a third started in sterile substrate from liquid culture I bought online that is still colonizing the bags. I don't need to try another and it could turn out to be a variety I already have. It might be a fun experiment though. Is there some way to get an idea if the mushroom mycelium growing is the mushroom variety you are trying to grow?
Knowing the fragrance is what I use most. I'm just a suburban dad who does this as a hobby and life extension. Maybe someone who does it semi-professionally or more would know more. You could use a microscope of course.