That's CH3-Br. A carbon atom having three hydrogens and one bromine atom attached to it.
Halogenation of hydrocarbons such as methane to provide bromomethane involves the gas phase reaction of methane and bromine, in the presence of ultraviolet light which acts as a free-radical initiator.
Thus, the precursors to bromomethane are bromine and methane.
Perhaps I mis-read, but I can in no way fathom how a seed oil would be used as precursor to bromomethane.