Hi Macernart, welcome!
I found that Begonia wightii is a synonym of Begonia maculata:
Polka Dot Begonia (Begonia maculata)
I bought the seeds from Mauro Peixoto, a Brazilian botanist. He sells seeds he has available at the time from the many species plants represented on his most interesting website:
http://www.brazilplants.com/me...
The photo presenting Begonia maculata on his site doesn't show the white dots, but don't let you be taken back by that, he explains that the plain green leaves appear in older plants. The flowers can be white, pink or red.
This is it in its natural habitat, the Atlantic Forest where I photographed them, you can see the dotted and the plain leaves in the same plant which was growing on a steep rock.
