Last but not least, my Kucle x Poncirus hybrids... Kucle is a cross between a Kumquat and a Clementine, so via Clementine also a cross with willow leaf mandarine.
All, except the plant below, are Poncirus hybrids.
Now look the plant in the middle of the next picture:
It has some trifoliate leaves - difficult to see on the photo, though. But nearly all leaves are monofoliate and quite narrow.
Here are some purely monofoliate seedlings from the same plant and year:
You see in the middle another plant with narrow leaves much like willow leaf mandarine. It seems to me that the feature of narrow leaves is (latently) present in Kucle and that it has the power to suppress trifoliate leaves. See also my post about Yuzu x Poncirus.
The growth rate of my Kucle hybrids is different. But many grow just as good as other Citrus seedlings. Some may be vigorious. It is difficult to say for sure when they are still so small.
About my pollination technics: Quite simple: I never castrated the flowers. I just took care that I pollinated before the bees were flying, i. e. early in the morning and several times a day as new flowers opened. Kucle usually has no pollen. It has only rarely got some flowers with pollen. So self pollination is not totally excluded but very unlikely. I had in the year of the cross some Citrus plants flowering in the same glashouse at the some time. But I had no Poncirus hybrids flowering.
I made the mistake that I placed my Kucle at a place much too hot. So growth was minimal that year and all fruits were only as big as small Kumquats (not even a third of the normal Kucle size). Yet all seeds were very well developed and germinated readily. Kucle is strictly monoembryonic and zygotic.
