Answer: Without knowing exactly which disease(s) affected your plants, I can't tell you whether you are battling blight, fusarium wilt, verticillium wilt, or something else. Diseases such as these can be in the soil, but they can also come in on purchased seedlings, be transmitted on dirty tools, be carried by insects or even in the case of blight possibly blow in on the wind. Daunting, isn't it.
You are right that it is a good idea to look for resistant tomato varieties; VFFNT types are available and would probably be a good idea since you have a history of problems. Be sure you are buying good quality, clean transplants. If you raise your own, disinfest all of your seed starting tools and materials and use fresh clean soil mix. Next on the list is garden sanitation -- clean up, remove and destroy every shred of spent tomato plant (including the roots and any fallen fruit) you can find. Do this every fall and, should a problem occur doing the growing season, remove and destroy any resulting plant trash immediately. Next, enrich your soil with copious amounts of organic matter, maintain adequate spacing between the plants, and ensure they receive adequate moisture and nutrients. Nature has its own way of helping to fight the battle and healthy soil and healthy plants resist problems far better than those which are less robust. And last of all, rotate your plants in the garden. Many gardeners find a three year rotation sufficient, but with a history of problems I would suggest a four year rotation for your tomatoes and their cousin members of the nightshade family: eggplant and potatoes. Good luck with your tomatoes!
Q&A Library Searching Tips