The following table shows the primary hybrids (species x species) between those species in the Sinningia clade most frequently used in hybridizing. This is not likely to be a complete list, but it should provide some guidance about what things have already been done. Notes for each species provide additional information about secondary crosses and other potentially useful information.
It is very likely that not all primary crosses between species in the Sinningia clade should produce fertile hybrids. Some certainly are, but the species are not as closely related to one another as those in the Dircaea clade.
Judging by the experiments of Peter Shalit and Dave Zaitlin, Sinningia speciosa, S. guttata, and S. lindleyi form fertile hybrids with each other and with each other's hybrids, through several generations.
Key to the table:
|X||hybrid of unknown fertility|
|?||Attempted or recommended cross|
Notes on primary hybrids
The cross Sinningia guttata x lindleyi was done by Peter Shalit. Peter reports that the hybrid is fertile, and he has selfed it, crossed it back to both parents, and crossed it with S. guttata x speciosa 'Carangola'.
The cross Sinningia guttata x speciosa 'Carangola' was done by Peter Shalit. Peter reports that the hybrid is fertile, and he has both selfed it and crossed it to S. guttata x lindleyi. Dave Zaitlin crossed this F1 to S. speciosa.
Dave Zaitlin has been doing a lot of work on S. guttata and S. speciosa as well. It is quite likely that the spotted "florist gloxinia" clones owe their decoration to an ancestral S. guttata.
The cross Sinningia hirsuta x kautskyi was done by both Mauro Peixoto and Dave Zaitlin. They agreed on the name 'Amizade' ("friendship" in Portuguese) for the hybrid. They both report that they have been unable to get seed from it, so it is probably sterile. This hybrid is reputed to be easier to grow than either of its parents.
I tried the cross Vanhouttea brueggeri x Sinningia hirsuta a few years ago. I got one seedling, which turned out to be V. brueggeri.
I tried the cross Vanhouttea brueggeri x Sinningia guttata in 2008. I did not get any seed.
I tried the cross Vanhouttea brueggeri x Sinningia lindleyi in 2008. I did not get any seed.
The cross Sinningia lindleyi x speciosa has probably been tried and accomplished, but I don't know about the results. Peter Shalit's results with three-species crosses (see above) strongly suggest that this cross should be fertile.
The cross Sinningia helleri x guttata was made in 2015-2016 by Hung Nguyen. He also obtained F2 plants from the hybrid, proving that it is fertile.
Jon Lindstrom did the cross Paliavana tenuiflora x Vanhouttea lanata, and obtained a plant with "reddish purple" flowers. The picture in the 2011 2Q issue of Gesneriads shows trumpet-shaped flowers with both solid dark lines and dotted lines, and some free-standing dots. Since this was apparently the first cross between Vanhouttea and Paliavana, Jon gave it the hybrid genus name of xVanvana. In reference to the intriguing mixture of dots and lines on the flower, he named the cross xVanvana 'Harlequinade'. It is probably best suited to greenhouse culture, as it presumably has its parents' aversion to subfreezing temperatures, and since it blooms in autumn...
Additional hybridization notes
Dave Zaitlin crossed S. kautskyi with S. schiffneri and named the resulting plant S. 'Carnaval'.
Paliavana tenuiflora has been crossed with a couple of species outside the Sinningia clade, resulting in plants which are no doubt sterile. The same is true of P. prasinata.