Hans Kylberg wrote:

>>I did come across the information that eggplants are native to tropical SE
>>Asia.
>
> That is what I also read, and in that case it is no nightshade.
> The article also told about the mistake when giving the latin name to it,
> there was an explanation for the mistake also. So it all seemed reliable.

Eggplant is not only in the nightshade family, but is even in the same
genus as potatoes and tomatoes (peppers are a different genus), so is
very closely related. Peppers, tomatoes, and potatoes are from the
Americas, but some nightshades are from the Old World. The eggplant
blossom looks very much like the blossom of common nightshade (which is
not American, btw). Here is a great resource, a searchable taxonomy
database:
http://www.ncbi.nlm.nih.gov/Taxonomy/

While looking up eggplant I was interested to learn that sweet potatoes
are related to potatoes, being in the morning glory family, which is in
the same order (solanales) as the nightshade family.