I'm wondering for some time.. How would mushrooms fruiting body call it own mycelium? Imagine you're that fruiting body and after releasing your spores you are about to die.
Truth is, the "mushroom" part of, well, the mushroom, is really only the fruiting body. This is like asking "how would the apple call it's apple tree".
If you want to have mushroom people which looks like mushrooms, you kinda have to forget about the mycelium and chalk it up to creative freedom, because the fruit of the mushroom isn't that big in comparison.
Mushrooms aren't plants. They don't use chlorophyll (well, lichen does, but it's a fungi and an alga teaming up so the fungi still doesn't chlorophyll). They get their energy from decomposing other stuff, which is something the mycelium does - of course.
The "me" of a mushroom should really be the mycelium. Still, to really give you an answer, if I was a mushroom I would refer to my mycelium as my roots.
Then die a gruesome death as I slowly rot alive.