Before we get to diseases, a planting question: Did you direct seed this plant or was it a transplant?

I direct seed these each year.

Peggy

More than likely it is Alternaria Blight. This fungus is most commonly found on the seed coat. Nothing to do now but discard the plant and the seeds you used this year and start with fresh seeds next year. One other thought, did you have problems with your tomatoes and/or did you leave the dead plants in/on the soil last year. If so this may be the source of this years infection. Only proper composting kills pest and diseases.