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? Is it an orchard or a single tree? What other species/organisms are nearby? Are the trees tightly spaced or well spaced? What is the weather like Hi temps? Lo temps? How deep is the freeze? How long does the freeze last? What other organisms including fungi live in the soil already? What does the soil consist of? How's the drainage? How much rain does the site get?
This is just the tip of the iceberg and only an example of the factors that may play a role in which fungi establish a symbiotic relationship with the trees. So when you buy mycorrhizae, to my knowledge, you get a great variety. You introduce them all and the best ones are the varieties that thrive survive multiply and get the job done.
This probably isn't the answer you were looking for and if not I apologize.