If it ws somehow in a bananas best intrest to remain "pure", they would not have evolved flowers that are so atractive to bees. This is a naturally outcrossing species that has few solid crossing barriers. There are no such thing as pure species in crops like banana, there is more realistically a continum of genetic variation. We just clasify things into discrete species because it is a convienient way for us to think of and describe the variation we see...In reality nothing is that discrete.
