Figure 1. The first symptom of Fusarium crown rot one of tomato is likely to notice is a wilted plant.
Figure 2. Dark vascular discoloration is typical of crown rot of tomato. Whereas vascular discoloration of crown rot typically extends an inch or two up the stem, discoloration due to Fusarium wilt will extend for several inches. Note also that wilt due to Fusarium wilt tends to be one-sided whereas wilt due to crown rot is likely to be the entire plant.
Figure 3. Canker on outside of stem due to crown rot of tomato.