Pioneer for DVD-R/RW mechanisms and Ricoh for DVD+R/RW mechanisms and Panasonic for DVD-RAM mechanisms.
The first recordable DVD formats developed by the DVD Forum were DVD-R, DVD-RW and DVD-RAM.
The DVD+RW Alliance, led by Philips and Sony, created a different format: DVD+RW and DVD+R. Both the DVD Forum (-R) and DVD+RW Alliance (+R) claim better compatibility kind of like the old days when Sony Betamax and VHS went to war.
Thankfully everyone decided to play nicely together and we the end users have benefited.