Tomato seeds and plants may be sold with a string of letters after their variety names. These are codes for disease resistance. Common letter codes include:
A Alternaria stem canker
F Fusarium wilt
FF Fusarium, races 1 and 2
FFF Fusarium, races 1,2 and 3
T Tobacco mosaic virus
St Stemphylium gray leaf spot
V Verticillium wilt
For example, ‘Early Girl’ tomato labeled “FV” is resistant to “F,” Fusarium Wilt, and “V,” Verticillium Wilt. Fusarium and Verticilium are common fungal pathogens in California soils.
Resistance is not the same as immunity. Tomato varieties may still be affected or even succumb to the diseases they are bred to resist, particularly when highly stressed by environmental conditions.
For a complete guide to growing tomato in your area, go to GardenZeus and enter your zip code, then go to tomato. For a helpful overview of the nutritional needs of tomato plants during the growing season see GardenZeus Tips for Fertilizing Tomatoes During the Growing Season.