@poorwolf, I grafted scion from my Northpole tree (whatever we want to call the generic) onto M27 and Bud9. I chose some smaller sized spurs (branches?) and used the tip, so the terminal bud was intact and formed the new tree. I don’t know how that affects take or subsequent growth, but they take just fine and grow just fine. The tree on M27 is about 6 feet tall in four years. I moved it, so it had a setback, but the apples that it made this year are as large and flavorful as the original. It will be a couple of years before the one on Bud9 is producing. Using narrower spurs as scion on pencil sized rootstock, the girth was about the same. Mine are whip-and-tongue grafts.
Now that I have RedLove® Calypso® and Redlove® Era®, I really want those to bloom next spring so I can pollinate NorthPole® and Golden Sentinel® with the pollen. I think it will be fun to see what happens - maybe one of the seedlings would be columnar, red flesh, and disease resistant? Of course flavor would be the most important question. An awful lot to ask from a too-small, very limited number of crosses, but it’s all in fun. I also have one-year-old Tasty Red® and Golden Treat®. They could be good as parents too, with disease resistance as the motivation. I do not know the flavor of those yet. They were developed in the Czech Republic by the late Jaroslav Tupy, who also developed the Opal® and Topaz® apples.
Golden Sentinel® and Scarlet Sentinel® originated at Summerland Canada as (Spur McIntosh Wijcik x Delicious) x (Discovery). Discovery is a UK apple, Worcester Pearmain X possibly Beauty of Bath. I’m not that crazy about using Delicious as a grandparent but they were once a good apple. The linked article stated that Discovery sometimes has pink flesh, but apparently that did not pass on to its columnar descendants. Wijcik McIntosh is just a columnar mutation of McIntosh so has the same flavor and other characteristics as its parent, just in columnar form.
It’s also interesting that the apple “Discovery” was a chance seedling grown by a fruit farm worker, not something developed at a university or government program.