I have had this Gymnocalycium for about a 1 week now. All seemed fine until last night. I was trying to decide how to repot it since it was not standing up in its pot it came in. I figured it was because these grafts are way bigger than thy usually are (4" pot and about 6-7" tall) I noticed the part below soil level looked paler than the rest. When I went to check on it today, there was rot on the stem portion that was under the soil and was getting mushy. I unpotted it, cut off the fleshy part that was mushy and removed most of the soil. I know these are cheap and silly but I really like it and want to save it. I have cut to the center stem part, cleaned the wounds and dusted with cinnamon. I know normally one cuts straight through the whole thing and let's it callus and then try to root the end of the rootstock part. I have the roots bundled in a paper towel. In case there is some way to save it roots and all. I know I'm being nutty so I don't mind anyone saying so :)

Any advice on how to save this one is greatly appreciated.