Perhaps breeding wasn't the right word. Many varieties vary by way of mutation when I single branch on a given tree has fruit of a significantly different quality. This is called a sport. When such a mutation is considered a useful improvment the discoverer can patent it and market it as his own. There are scores of seperate patents on different strains of Red Delicious for example.
[NAFEX] breeding the russett out,
Alan Haigh, 11/13/2007