http://www.occupymonsanto360.org/2012/03/06/monsanto-free-seed-companies/
"First, to explain: there are thousands of other seed companies out
there that have also signed the Safe Seed Pledge and/or might even be
organic. However, Monsanto purchased Semenis which was (and is) the
world’s largest seed company and now they own thousands of
conventional seed companies in addition to their GMO seed business.
Monsanto now owns 40% of the conventional seed market in the US and
20% of the worldwide market, including organics and heirlooms. It’s
not terribly easy to avoid them, which is why we’ve compiled this list
with the help of readers and some experts from the field, both to help
you navigate through things as well as encouragement for companies to
take part in the boycott so that they may also qualify to have their
names included."