In article ,
Stewart Robert Hinsley wrote:

The following page gives a subgenus name

http://www.intl-pag.org/8/abstracts/pag8311.html

but you probably want something more specific like a section or series.

Thanks! From this I determined that eggplants are in the subgenus
Leptostemonum, which helped me find some excellent links on eggplant
taxonomy. Subgenus Leptostemonum has only about 200 species, while
the whole genus Solanum has an estimated 1000-2000, now that they've
glommed Lycopersicon and some others into it. There's a multi-center
project on to create a worldwide taxonomic monograph of the species
Solanum. It has a web page at the Solanaceae Source web site at
http://www.nhm.ac.uk/research-curation/projects/solanum.

I'm just about sure now that the plant I'm growing is S.aethiopica.