Makrut Lime leaf irregularities

[mountaingoat]

I purchased a small Makrut lime tree about a year ago at a nursery near where I live in Southern California. The first spring I had it (2020) it sprouted this strange branch. Instead of the typical double lobed leaf, this branch's leaves have tiny, non-winged petioles and trifoliate appearing leaves. I have done several thorough google searches to try and figure out what happened to them, but I have been entirely unsuccessful. Out of curiosity, I have allowed the branch to remain on the tree (despite being located far below any of the other branches) and I will let it bloom (and maybe set fruit) in the spring. But I have another month or two to wait still, presuming the branch even flowers, and I am very confused about what is going on. I looked into it being a mutation or a disease, and I have considered the possibility that it is was grafted on by the nursery (for what reason?). I was hoping someone here had seen something like this before and could offer me some insight. I have attached photos of the affected and regular leaves for reference, as well as the spot where the branch joins the trunk. The leaves were slightly damaged by hail last week and the tree was living with minimal sunlight for most of the last three months due to a move, but otherwise it seems fairly healthy to my limited knowledge.
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[Laaz]

Your tree is grafted. The round circle is your graft line. Being you're in Southern California, the roostock is probably C35.

[mountaingoat]

Thank you!

[citrange]

To elaborate a bit on Laaz's answer.
Most citrus plants are propagated by grafting on to a rootstock.
This can provide advantages such as cold tolerance, disease resistance, soil type tolerance etc.
Many rootstocks are seedlings of Poncirus trifoliata or its hybrid descendants.
Many of these, including C35, have trifoliate leaves.
If you allow the rootstock to sprout and grow from below the graft line, this shoot will grow vigorously and deprive the top variety of strength and nutrients.
Unless you really want to grow the rootstock rather than the top variety, these shoots should be removed.

[poncirusguy]

why is C35 used everywhere.  Any citrus trees I get should be on PT or flying dragon.  One Green world is the only one that uses FD.

[lebmung]

Jan 8, 2021 14:53:10 GMT -5 poncirusguy said:

why is C35 used everywhere.  Any citrus trees I get should be on PT or flying dragon.  One Green world is the only one that uses FD.

Kaffir lime shows extreme benching on FD, I have several trees. Also it makes them drop leaves in winter.

[millet]

All trees on Flying Dragon show benching.  Bud union typically show considerably shoulder development, which sometimes leads to compression girdling  The problem of compression girdling normally only occurs with mandarins.  Most all mandarins perform well for at least 10 to 15 years but eventually develop bud union crease and decline. Overall an excellent rootstock where it is well adapted.  Disease resistance makes it a good choice for replant situations.  CPM