My aubergines are used to be eaten by local hungry Colorado beetles. It seems to me they like aubergines much more that potatoes ;-)
Best and most prolific aubergine varieties I grow:
Almaz (translated as "Diamond" in English) - 60-75 days, a compact and standard variety here. Ukrainian/USSR CV.
Little Fingers - 70 days, I like multi-clusters.
Patsekha ("Fun" in English) - 55-70 days,earlier than Black Beauty, Belarusian CV.
Lebedinyi ("Swan" in English) - 55-70 days, white skin, bitter-free, Russian CV.
Kashalot (=Cachalot in English) - 50-60 days, the most vigorous and prolific Russian aubergine. See it on the picture below:
I have trialed many aubergine varieties, but don't think it is a good idea to grow them in Zone 4a even in greenhouse. Beetles, low production and luck of space say it all.