Pokemon can learn HMs and TMs by breeding, but only if the father knows them. Since the Bellossom you taught Toxic to is female, then there is no way to use it to get an Oddish with Toxic.
However, that doesn't mean there is no hope. Roselia learns Toxic at level 45 naturally. So get a male Roselia, level it up until it gets Toxic, and breed it with your Bellossom (they are both in the grass egg group). The resulting Oddish should know Toxic.
Check out the breeding page on this site for more information on breeding. The section titled "Passing Down Moves" is the one of particular interest for this question.