What breeds of horses make up the apploosa breed?

The American Appaloosa is now considered a purebred and therefore only two approved, registered, and DNA tested Appaloosas can produce and appaloosa foal.However some registries may only go by color, so any two horses that produce and appaloosa or 'leopard' patterned foal could 'create' an appaloosa.
In the past before the ApHC (Appaloosa Horse Club) was founded, a handful of people decided to save the old Nez Perce indian pony, which carried the leopard complex gene responsible for the spotted coloring of the Appaloosa. The US cavalry had destroyed most of the tribes purebred horses and bred the remaining ones with large, slow draft horses. The people added Thoroughbred, Quarter horse and Arabians to a degree to lighten up the now draft like breed and to 'modernize' it for ranch work and circus shows.