I have seen some of JR's videos before. I did not realize that he had a nursery. It is quite remarkable to see what he has throwing fruit there in Orlando. I wonder if he grows anything on standard roots.
It seems interesting to me that many apples found in low chill areas are seedlings. Granny Smith pops up quite a bit in the family tree, too. The Revrend Morgan apple from Houston, Texas (for example) was a Granny Smith seedling.
Eliza Greenman (Hog Tree) has some very interesting thoughts on the topic...
"The Fruit Explorers, a group of which I’m a founding member (along with Pete Halupka of Harvest Roots Farm and Ferment), traveled around the South last year looking for all sorts of apple trees. By far, the healthiest trees we found were those on standard rootstock or growing on their own roots. We were in the hot, humid, zone 7a-8a South which is known for all sorts of rots, fireblight strikes, fungal infections…you name it. And the trees that looked the best were the big ones. All of this observation caused me to believe that we probably have the best chances of growing low-input trees if they are on big roots."
Here is the link to the rest of the blog.
https://elizapples.com/tag/root-graft/ Everything she says makes sense to me. Very occationally you find an old pear tree around here. They are grafted to Callery pear (standard) roots. I've never found an "old" apple tree around here and I can assure you it was not for lack of planting. Is Malus doumeri var. formosana the Callery pear of apples (hopefully without the invasive tendencies)?