Here is how genres work in FUGA:
Genre - this field contains broad genres that are accepted by all stores; this is to ensure that your product will be delivered with a genre. This field is not editable, so you cannot add a new genre, you can only select one from the list provided.
Sub-genre - this field can be edited, so you can add your preferred genre here.
The same applies for the Alternate genre and Alternate Sub-genre fields.
Full Apple Genre and Sub-genre list here: https://itunes.apple.com/us/genre/music/id34
Apple Track-level Genres
FUGA sends track-level genres for current Apple deliveries