hi redbaron -
I have started LA1777, a high altitude accession of Solanum habrochaites (or Lycopersicon hirsutum) to use and it sets clusters of flowers. The species is indeterminant.
The photo is of an excellent cold-tolerant variety of cherry tomato I was thinking of trying in a cross. Koralik also has a very high sugar content. Another variety to use might be Nepal which will set and ripen under very cool conditions.
Crosses made to wild species should show an improvement in cold tolerance, and I plan to include tomato varieties which already demonstrate some resistance.
Wild species like LA1777 close their stomata during chilling, preventing wilting. But their root systems also will grow in cold soils, so it might be interesting to attempt grafting as well.
Here is a link to some research on this topic.
www.tuinbouw.nl/files/page/Bijlage%203_10450-04_1.pdf
I need to wrap up this semester, and then I'll be working on this and some other projects.
Lee