Can your sulcata mate with your desert tortoise?

Possibly but unlikely. Both have 52 chromosomes but it isn't that simple. Sulcata are much larger so there may be physical limitations and while Testudines are genetically conservative (meaning they haven't changed much), the fact that the species evolved on separate continents could present problems. Even if you were successful, the offspring may be sterile and unable to reproduce (like a mule).