Question regarding Citrus

Does anyone know what rootstocks are more commonly used to graft Calamondin scions onto? I have a Calamondin which has been defoliated in the cold spell we had in the Spring (-5C/23F), and is growing back like a champion... however the cold has triggered regrowth of the rootstock.

It would be handy to know the most commonly used rootstock.

I know Poncirus is used frequently - however it's emerging rather later, and my assumption is that if it was Poncirus it would have emerged earlier on (but maybe it can emerge later?)

 

Poncirus has trifoliate leaves, so is easily recognisable.
I think it is quite often pretty late before citrus start to make new root, I find new top growth is very possible without new roots.
I grew poncirus outside for many years and new growth was earlier than this, but if the calamondin is still alive, then maybe the sap would mostly move up to that first.