Hello JemsInc and Pasi,
Regarding to the parentage,
1- it may be a pumello hybrid (
Citrus x
grandis). It is also named Sanbokan Grapefruit. (
Citrus paradisi certainly also being a
Citrus grandis hybrid)
2 - The International Plant Name Index says
Citrus grandis Osbeck var.
sulcata is a synonym of
Citrus sulcata.
That's a second hint of this
Citrus parentage with pumello and/or grapefruit, rather than lemon. Maybe a pumello x lemon, lemon x pumello, grapefruit x lemon, lemon x grapefruit hybrid?
BTW, there is not much information about that
Citrus, indeed. Maybe you've seen that page?
http://www.woodlanders.net/index.cfm?fuseaction=plants.plantDetail&plant_id=1144Regards
Laurent
Regards,
Laurent