Not sure what you are trying to say. I assume you want to root some
cuttings from those trees. These will after a few years become fruit
bearing trees.

If you truly want to propagate rootstock (grow cuttings from those
trees so you can graft scion onto them), you are saying you think
those trees have excellent root characteristics that you want your
apple tree roots to have. For example you might think those tree
roots do well in poorly drained shallow soil and you want that.
Cuttings will work if those trees have their own roots and were not
grafts.