That's interesting that you breed fruit. I also grow lots of different fruit types (pear, apples, peaches, plums, pluots, cherries, walnuts, kiwis, nashi, citrus, pawpaws, persimmons, pomegranate, etc..) but haven't got to try and breed them to obtain new varieties.
I have 500+ fruit trees (not counting fig trees) but, lately, i am also using established rootstocks and multigrafting varieties on them (i have several pears, apples, plums and peach trees with 5-6 varieties grafted) to be able to evaluate quicker what i really like and what adapts better to the conditions i have. In the established rootstocks i used chip-buds, whip and tongue and bark grafts. In peaches the chip-buds had the lowest success rate of the three techniques (many took but some didn't develop, even when the competing original buds were removed from the branch - i left several original branches untouched and that may be the problem)