Potatoes and tomatoes cannot be cross-bred. However, it is possible to graft the shoot of a tomato to the rootstock of the potato plant. The grafted resulting plant can successfully produce both potatoes and tomatoes. The draw for grafting the two plants is for space purposes. It saves space and helps a tomato plant grow where it might not normally be able to. Grafting the two together can affect the flavor outcome of both vegetables.
The easiest way to graft the two plants together is by finding potatoes and tomatoes with very like-sized stem and root. The potato stem should be cut into a “V” and then cut the tomato stem to look like a wedge that fits the “V” you already cut. Slide the two pieces together and wrap with grafting tape and voila! You are on your way to a totato or a pomato plant.