Cloning Rootstock

So I've got a semi-dwarf (Moonglow) pear tree which has a root stock sucker coming up. I'm assuming it's quince, but not sure. I've heard that you can clone root stocks by layering the sucker like you do a currant. Is this true? If not, should I leave it and see what fruit it'll bring or is that just a bad call?

well for sure dont let it grow out.

so you can cut it and compost
cut it and root it
or if its long enough layer it

i just put mine in a mist propagation system.