Tunastopper makes a good point. Are turkeys one species with several breeds, like dogs, or are turkeys one breed with several colors, like Labrador Retreiver. Some of the things that separate breeds are size, temprament, behaviors, different shaped heads or tails. Turkeys are all about the same shape, they're mostly friendly, and they are all really fun to watch. So in that respect, turkeys behave like a single breed. But some kinds of turkeys are smaller than others, and those smaller sizes seem to be linked to color, such as royal palm and midget white. In this sense, some turkeys seem to behave like different breeds.
On the whole, though, I think I will have to agree with tunastopper and suggest that we could treat turkeys as different colors of a single breed of bird. Labrador retrreivers can be bred to produce lines that are all yellow, or all brown, or all black. But when you mix 'em up, you can get yellows that throw blacks and browns, and we still call 'em labs. Oops, that's not true, yellow cross yellow is always yellow, but you can get blacks or chocolates that throw yellows.
Broad-breasteds might be considered a different breed since they have been selected for a trait, and that trait has been so developed that they ar no longer the same as heritage turkeys. Could wild turkeys also be considered a different breed than heritage turkeys?
Interesting things to consider.