  We systematically investigate the transmission of charge carriers across the
grain-boundary defects in polycrystalline graphene by means of the
Landauer-B\"uttiker formalism within the tight-binding approximation.
Calculations reveal a strong suppression of transmission at low energies upon
decreasing the density of dislocations with the smallest Burger's vector
${\mathbf b}=(1,0)$. The observed transport anomaly is explained from the point
of view of back-scattering due to localized states of topological origin. These
states are related to the gauge field associated with all dislocations
characterized by ${\mathbf b}=(n,m)$ with $n-m \neq 3q$ ($q \in \mathbb{Z}$).
Our work identifies an important source of charge-carrier scattering caused by
topological defects present in large-area graphene samples produced by chemical
vapor deposition.
