This is very interesting. I was cutting some very small pieces off two Ichangquat seedlings, and I decided to crush up the leaves and noticed they had a different smell.
All the other Ichangquat seedlings have kind of a skunky smell, like mustard seeds or boiled cabbage, that isn't too pleasant, but these two smelled distinctly different. (Perhaps not coincidentally, these two Ichangquat seedlings also seemed to have a visibly different phenotype from most of the others also)
The first Ichangquat seedling displays very dark colored leaves, and the leaf shape is a little more stubby, as well as looks thicker. I hate to speculate, but I really suspect this Ichangquat could be a tetraploid.
The leaf smell of this Ichangquat is beautiful, like the smell of citron leaves and Ichang papeda. It was almost lemon enough that it might be appropriate for culinary uses, it seemed like. Doesn't have any of the skunky smell.
The second Ichangquat seedling is the one I suspect could have been pollinated by citrumelo (and thus, if that's the case, it would be an Ichangquat x citrumelo hybrid) because I observed two small leaves on the plant that displayed bifoliate characteristics, though all the other leaves so far have been monofoliate. The leaf color also looks a bit lighter than the other Ichangquat seedlings.
This one has a slight but distinct smell to its leaves like spearmint or basil, something in the mint family, maybe lemon verbena. There is a very slight skunkiness in the background, but it's less than half as strong as it is in the other Ichangquat seedlings.
I don't think this holds true very often, but I believe in this case leaf smell could be one of the characteristic traits used to help differentiate seedlings, to see if it was a zygotic seed with different genes than the parent.
It's very interesting, if only a slight curiosity.
I've never smelled leaves from any other citrus that were quite like this.