Compare the description of an MBR partition table entry with the description of a GPT/GUID partition entry. You'll see that while the GPT/GUID partition has dedicated locations to have both an "unique partition GUID" and a "partition name", there none of those available for MBR. So you just can't do this on MBR, it's available only for GPT.
There's still an unique 32bits identifier for the whole MBR (at position 0x1B8) that might be usable, along with the partition number. It can be changed using fdisk's expert options:
# fdisk /dev/ram0
Command (m for help): x
Expert command (m for help): i
Enter the new disk identifier: 0xdf201070
Disk identifier changed from 0xdeadbeaf to 0xdf201070.
Expert command (m for help): r
Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
What you should probably use, like with tune2fs for ext2, is jfs_tune to label the filesystem. For example:
# jfs_tune -L mylabel /dev/ram0p1
jfs_tune version 1.1.15, 04-Mar-2011
Volume label updated successfully.
# blkid |grep ram0
/dev/ram0: PTUUID="df201070" PTTYPE="dos"
/dev/ram0p1: LABEL="mylabel" UUID="e1805bac-44fb-4f4e-860b-64a1d303400f" TYPE="jfs" PARTUUID="df201070-01"
All "variables" output by blkid are probably usable in
/etc/fstab, you should do tests.