Looks like man made damage to me… like someone took a hatchet to it.
What is all that on the left… blue white black… jammed into the rootstock ? I see numbers on part of it…
TNHunter
yep. looks like the trees growing into whatever that is on the left.
Can we get a zoomed out photo? Or description of what’s going on that you’re concerned about.
Sometimes, when there is heavy rainfall and high nutrients, tree trunks can get splits. The splits are normally vertical and not horizontal. Sometimes, fruit splits as well. Splits indicate very rapid growth typically during hot temps or following dry periods. It would help to know more about the rootstock and scion and the big picture always helps. Is the graft union right there? How old is it? Are the graft and scion fully compatible. Im guessing you put a 2023 piece of cardboard as a back drop to show us the crack better. Im guessing you also pulled the dirt back aways to see what was going on there. Im guessing that is the graft union and the bottom is outgrowing the top.
That was some great detective work there. It was very impressive. After double checking, the 2024 vintage cardboard is indeed a slightly darker shade of blue. 
Thanks for the reply and sorry for inconvenience
Actually it is second year of hd plantation of gala apple on m9 root stock. How these cracks can be closed? Any solutions. Cardboard in the backdrop is just for clicking good picture.
Furthermore the crack is occurring just at the graft union of plant
I think the root stock may be overgrowing the Gala - is that possible?
Your options are limited. I would not water it though i suspect it is wet there. One option is to create a dirt mound around the tree and mulch it well burying your problems and possibly rooting the scion. Another option is to leave it alone chancing it will rapidly grow back together. A third option is grow another roostock beside the first one and eventually fully bypass grafting it over to the more compatible rootstock. I would suggest painting the trunk again. If im correct and it is hot and wet there the trunk may also be getting some sun burn. If that is true the crack will remain isolated to one side of the tree. Even shade cloth on one side would cool the trunk down some. The simple truth we all know well is that might not be the best rootstock for this scion in this climate.
“Based on my diagnosis of the picture and previous experience, I believe this is root gall disease caused by the bacterium Agrobacterium tumefaciens. This disease appears as rough nodules at the base of the stem or root, and affects the growth of the tree. There is no effective treatment for it, so it is recommended to remove the infected tree, sterilize the tools used, and avoid planting in the same soil for a period of time, to prevent the spread of the infection.” This happened to my grapevine. I got rid of it and disinfected the area to avoid infection. I planted flowers in its place that are resistant to this infection. If there was a clearer picture or an accurate description so I could confirm that.
It could just be a growth event caused by excess sap rising during sprint awakening from dormancy. If you are not aware of what caused the crack, then I would disinfect the trunk with warm soapy water, let it air dry and use a strip of plastic 1-2” wide to wrap it up tightly so the bark can regrow without the possibility of getting infected. After a 2-3 week period normal callousing should heal the wound, so remove the plastic strip to prevent girdling and re-examine to assess healing. By that time the gap should begin to close if it heals properly. Keep the wound covered with a clean plastic wrap until the gap is closed and bark grows over it.
Dennis
Kent, Wa
I can’t tell much from that photo… but graft union failure on M9 is not an unknown phenomenon.