This project has inspired me to try a similar experiment.
Three years ago a natural and unexpected cross between 'Mexico Midget' and/or both 'Brandywine (Sudduth)', and 'Italian Heirloom' occurred in my back vegetable plot. The next year (2014) hundreds of little vigorous tomato seedlings appeared and we let a good portion of them grow to maturity, and we had this small-to-medium sized red tomato that was pretty darn tasty and enjoyed by everyone we shared with.
In 2014, we planted other varieties in the back garden with our "wild" tomato variety. I expected and hoped for some crosses to enhance genetic biodiversity, but in 2015 when the wild tomatoes came up they were the same as the year before, and as far as my eyes and tongue could tell, were no different than the year before. I found this strange, because as far as I know, F1 hybrids, don't usually grow true. Perhaps some other genetics ended up getting in there after all.
After reading your posts and work, I see now that most cultivated tomatoes have poor flower structure for pollination and are natural inbreeders. I searched a rather massive database of wild tomato accessions and have selected quite a few to evaluate and incorporate into my tomato population.
I selected accessions that had the following characteristics:
Pollinators noted visiting flowers
Large Flowers, or high amounts of flowering
Disease or Pest Resistance
Cold, Heat or Drought Tolerance
Good Fruit Sets
Flowering and Fruiting Time of Year
I have made selections from:
These 5 are listed as easily hybridizing with S. lycopersicum (common cultivated tomato), and according to my research can either be inbreeders or outcrossers, depending on the form.
They have a host of other helpful characteristics I'd like to incorporate like disease resistance, pest resistance, drought, heat and cold resistance, depending on the species and collection in question.
I also included the 4 species that make up the S. peruvianum complex:
Also useful for disease resistance and all natural outcrossers, as far as I can tell. From the information I could find this complex does not easily hybridize with S. lycoperiscum, and that:
Crossing L. peruvianum to L. esculentum (S. lycoperiscum) is rarely sucessful. Attempts frequently result in embryo or flower abortion. As more lines have been evaluated, a few have produced at least one seed. Fortunately, these hybrids are capable of backcrossing to a L. esculentum (S. lycoperiscum) parent.
Another method which has been successful at overcoming the incompatibilty between the cultivated tomato and the L. peruvianum is the use of L. chilense as a bridge species (L. peruvianum is crossed to L. chilense and that progeny is crossed to L. esculentum). Although this might seem encouraging, most of the time this methods fails, but does yield better results than a direct cross. Most crosses between the cultivated tomato and the members of the "peruvianum-complex" fail due to some sort of incompatibility.
Apparently S. peruvianum complex and S. chilense can cross, but I forgot to acquire S. chilense seed, so that won't happen this year.
I'm not doing any embryo rescue techniques, but hopefully one of the four species I'm evaluating will produce at least a little viable seed for further backcrossing.
I have concerns with flowering time as you have mentioned, but also edibility of the wild species I am crossing. I know I will end up crossing these wild tomatoes many time, therefore diluting any possible toxic compounds, but alas I could find very little information on edibility or toxicity of these wild tomato varieties. There are a lot of toxic members of the nightshade family and I'd hate to create something that got me or someone else sick. Some of the accessions I requested were noted as being edible by local peoples though.
I selected accessions with a diverse flowering time from Summer and Winter, taking into consideration that the Southern Hemisphere has different seasons. I have grow lights if necessary.
I also will be growing 8 conventional varieties, some hybrids, some open-pollinated, with some noted for producing lots of flowers, or lots of pollen, for an addition of genetics into my local landrace. I may have to hand pollinate, but I'm lazy and wish the bees would do this for me.