rustica

This defence against insects presents nicotiana with something of a
predicament, because it doesn't seem to be very good at keeping the
nicotine out of its nectar, or at least not completely. Thus, although
nicotiana nectar does contain less nicotine than the rest of the plant,
the two levels are still related; species with lots of nicotine in their
leaves also have relatively high levels in their nectar – high enough to
deter most pollinators.

Some species have decided to tolerate this limitation to their defensive
armoury and have relatively low levels of nicotine. But others have
really gone to town on the nicotine, avoiding the risk of poisoning
their pollinators by evolving self-pollination. No longer reliant on
pollinators, such species can have as much nicotine in their leaves as
they like – in practice, about 15 times more than the species that still
depend on pollinators. Nicotiana rustica, whose leaves can be up to nine
per cent nicotine, has gone down this route.
http://www.telegraph.co.uk/gardening/gardeningadvice/10173025/The-toxic-charms-of-nicotiana.html