I personally have little practical knowledge of grafting tomatoes, but our user here
b54red used to post often about grafting tomatoes in the south for disease and may have info of use to you.
Here are a couple threads
http://www.tomatoville.com/showthrea...ting+rootstock
http://www.tomatoville.com/showthrea...light=grafting
You should be able to find more by using the advanced search function here and his user name
b54red with "rootstock" or "grafting" terms.