>>489822Isn't there a problem with at chemical communication between the roots and the leaves of potatoes and tomatoes that prevents successful and vigorous growth of fruit or tuber of one or the other? I think it had to do with getting just the right varieties of potato and tomato that can work properly with each other. the only one I know of for sure is the TomTato.
Well, I answered my own question:
http://www.fastcoexist.com/3018867/meet-the-tomtato-the-worlds-first-combination-tomato-potato-plant 