Hello, I discovered that Gparted writes to the MBR (0 to 446 sectors) when it is empty.
Yesterday i used a live cd of ubuntu to delete a partition of my disk with Gparted. And my pc didn't boot after that. My os is a Fedora server installed in UEFI. Note that Grub is not installed in the MBR or in the partition. I don't know how but it boots fine like that. So i had to delete the code Gparted writed in the MBR (0 to 446 sectors) to boot again ("sudo dd if=/dev/zero of=/dev/sda bs=446 count=1"). I think Gparted should not touch the MBR (0 to 446 sectors) when it is not ask by the user. Thanks Thomas