Hello,
It look more and more important to hybrided the tomatos: this year is the pur exemple.All my tomatos have caught the blight this year and i have see most dangerous i have note that a few tomatos under a shelter have a few leafs with the blight.(this shelter is may old not totaly waterthight.)
The blight is not the alone problem for example: resistivity at the mosaïc, shadow, cold, hot, drought, rain
I don't demand a tomato totaly resistiant i have understand it impossible, the most resistant tomatos today could be the less resistant tomorow i want just more diversity on my patch.
For realised this experience, i will take a few cutings of tomatos or sow a few tomatos (if the plants are too sick) that i will isolated in pot.If it possible i will put this pot at a placement without wind for avoid the autofecondation.If a fruit get fat i will know easily if my fecondation is good.