We are very interested in your tomato problem and would like to follow-up with you.  You have done some good research and have made the proper conclusions based on your tests.  We would like for you to try one other technique.  Select a stem that is just below the wilting portion of the plant and gently slice back a thin section of the epidermis.  Note any discoloration.  
Note: Fusarium wilt begins at the bottom of the plant and works its way upward.  Verticillium wilt begins at the top of the plant and works its way downward.
We would like to see some photos of the plants.  Please indicate the varieties of the plants that are affected, and it may help to know the source of the plants.
Please monitor the plants and keep in touch.  
LS

The entire plant is wilted, but I have sent a picture of a cross section of the stem of the one I tested yesterday. The plants are Better Boy and I think I got them from another Master Gardener who started them from seed.

It would be helpful if you could take a sharp knife and vertically slice the epidermis of an infected stem. If the tissue directly below the epidermis is brown the plants are possibly infected with Fusarium wilt. Better Boy is resistant to race 1 but not races 2 & 3 of this disease.

Are any other tomato plants showing symptoms? Are they a different variety? Is the soil poorly drained where the affected plants are growing? Were there any problems in this part of the garden last year?  Please let us know. If we can't diagnose the cause we may ask you to pull up a plant and submit it to the Plant Diagnostic Lab on campus.
Jon 

I did this and did not see any discoloration. There are two other Better Boy but not right next to these. Next to them is a Roma and a Juliet. There were no problems last year, The soil is well drained. I have been gardening there for years and have improved the soil yearly. I have not done a soil test in a few years however.

thank you for your patience.  Our vegetable specialist took another look today and now suggests that you should send a sample to the Plant Diagnostic Laboratory on campus.   it will be necessary that you remove an entire plant and brush off as much soil from the roots as possible.  Wrap it in newsprint and place it in a suitable box.
The sample submission form and the address is provided on the following page:
https://extension.umd.edu/sites/default/files/_docs/programs/plantdiagnosticlab/PDL-plant_problem_su...
Please make a note that "Jon, at HGIC, suggested that this sample be submitted for diagnosis."
LS

I will pull it this afternoon and try get it to the University today or tomorrow, I thought the answer was probably from Jon. I know Jon well. Sue

We will await the test results.


ro