Managing the content of articles when a plant product (whether food or other) is not in a 1:1 relationship with botanical taxa is always a problem. Here it seems clear that a separate article on the plant product is the right approach; there's bound to be some overlap with genus/species articles. This article seems to me about right in its focus on what English-speakers normally mean by "banana", namely the food, where it comes from, what it is, how it's grown, etc. It would be possible to move some the taxonomy material to Musa (genus) perhaps, with some cross-referencing, so that the article concentrates more on the food and agricultural aspects of the topic, but this would be a marginal change.