  We study charge and spin transport along grain boundaries in single layer
graphene in the presence of a quantizing magnetic field. Transport states in a
grain boundary are produced by hybridization of Landau zero modes with
interfacial states. In selected energy regimes quantum Hall edge states can be
deflected either fully or partially into grain boundary states. The degree of
edge state deflection is studied in the nonlocal conductance and in the shot
noise. We also consider the possibility of grain boundaries as gate-switchable
spin filters, a functionality enabled by counterpropagating transport channels
laterally confined in the grain boundary.
