[FredB]

I have been trying various interspecies crosses, and my experience is similar to Joseph's.

Crosses that didn't work for me: arcanum, corneliomulleri, pennellii, peruvianum. In each case I used Brandywine as the male parent and the wild species as the female parent. The peruvianum cross produced fruit, but the F1 seemed to be sterile. Several of these crosses have been successfully carried out at research centers (google "TGRC introgression" for examples), but they seem to require more skill or persistence than I could bring to bear.

Crosses that did work:

S. pimpinellifolium. This one is easy. The success rate is about the same as what you get when crossing two varieties of domestic tomato. Some interesting properties of the F1 and beyond include intense red or pink color, intense flavor, high sugar content, and partial resistance to leaf and root diseases. I'm still trying to stabilize combinations of these features.

S. galapagense. A relative of S. pimpinellifolium, with tiny yellow fruit, frilly leaves, and a strong "burning garbage" smell to the foliage. The F1 fruit have a funky taste, but you can select that out in the F2 or F3 generation. I haven't noticed any special disease resistance, and overall this cross seems less interesting than the S. pim cross.

S. habrochaites. I got one successful cross out of about 40 tries. I used the habrochaites flower as the female, and I think the very long pistil is very sensitive to damage during emasculation. I tried crossing using intact female flowers in the greenhouse where there aren't any pollinating insects, and several of the attempted crosses took, but I won't know until this summer whether they are out-crosses or just self-crosses.

First, I'll explain why I'm interested in habrochaites, and then I'll describe the results of the cross.

A few years ago, just for fun, I tried growing out one of the rootstock tomato varieties, Emperador Hybrid. It was clearly habrochaites, not lycopersicum. Typical habrochaites characteristics included fuzzy leaves and stems, characteristic habrochaites smell, and large flowers with orange anther cones and long exserted stigmas. The fruits were round, 3/4", green when ripe, and were sweet but with a woody texture and flavor. The plant was huge, with a 1" stem, and it kept growing rampantly until frost, while my heirlooms and hybrids usually died by the end of August. It was totally impervious to septoria leaf spot, and had partial resistance to early blight. I figured it could be a good source of disease resistance.

Emperador Hybrid seems to be a cross between two habrochaites lines. The F2 plants were all clearly habrochaites, but they varied in stem and foliage color, hairiness, and early blight resistance. Since then, I've grown out several other Syngenta rootstocks and they all seem to be habrochaites (Arnold, Colossal, DRO 141TX, Estamino, Maxifort). They differ slightly in a few characteristics such as purple coloration of the stems, but they are all very similar. They all have rampant growth and appear to be completely resistant to septoria leaf spot. DRO 141TX seemed to have the best early blight resistance, so I am going to focus on using it as a parent in future crosses.

My successful cross had an F3 offspring of Emperador Hybrid as the female parent and Brandywine as the male. The foliage looked like lycopersicum but smelled like habrochaites. Out of four plants, two died in August and two survived until frost, so there seems to be some heterogeneity in disease resistance. Although Emperador fuit are green/yellow and Brandywine is pink, the F1 fruit were orange. I presume each parent was defective in a different step of the pathway for orange coloration, which would mean that the F1 would have all the necessary enzymes and thus could make orange pigment. The fruit are about the size of a golf ball and are netted like a muskmelon (see photo below). They are edible but the taste is a bit odd. At this point I have F2 seed and plan to select for a combination of edibility and disease resistance.

The fruit shown in the attachment are immature and don't demonstrate the full orange color.

Fred