I've never heard the term "breed" used for species of reptiles. I've heard of dog breeds, horse breeds, goat breeds, cat breeds, but never breeds of reptiles...
And generally with the different dog breeds you get physical changes, such as coat color, size, conformation in general, etc... To get a "pure" breed you have to keep line breeding until all the offspring produced look identical. Although classified as the same species, I would personally classify different "breeds" of dogs similar to subspecies.