My new muscadine developed an issue on the trunk earlier this year. I thought something had scratched it but it has continued to stay and get larger over the last several months. It started as split bark like you see on freeze damage but is getting worse. It is not freeze damage, it started early summer. I will go out later and get a better picture if needed.
It might be stretching out a bit as it grows and heals. Unless such a wound is close to completely girdling the trunk I would ignore it.
It could be growing pains as Scott mentioned but to me it looks like it was bumped by something hard enough to remove the bark. Either way I would also think with time it will heal over. Unsolicited opinion. Those lower leaves look pretty rough and I think I would carefully remove a few near the soil level. Hope it recovers. Bill
c5tiger, I`m in agreement with Auburn something may have sideswiped it. Appears to be starting the healing over process judging from the pic.As for the leaves we are into September and the older/lower leaves could just be starting the going dormant process. Muscadines are quite resilient so most likely its going to be just fine! Hope it recovers totally. Randy/GA