What a great question. It really got me interested in this. I have a biology background and even now as a forester, apples are still among my absolute favorite trees.
I did a little bit of digging and found what may be some good information for you.
This one cites Pitholithus tinctorious.
And this is from the Journal of American Society of horticultural ...
The one(s) that survive/thrive in your orchard. I don't know the specific answer to this and I don't know that anyone does. The reason being that "apple tree" and mycorrhizae are not the only variables in this equation.
What variety of apple tree? Are the trees healthy? How old are they? Is the orchard neglected or intensively maintained? ...