shunshun, I hope that if you are going to plant these, you have tested them in your soil, the fact that they may tolerate cold better is only one item to determine the usefulness as a rootstock. Another point is that openly pollinated seeds depending on where they are coming from, could be very unique and different from each other.
I have tested, Mexicola, Poncho, Monte de Oro (a Criollo) seedlings grafted on commercial varieties, and they don't do well in my soil, weak small trees, elements deficiency ect. You can graft them on Waldin and they grow great. I would hate to plant so many seeds only to find out they don't work in my soil.