  Aiming at understanding the origin of the electronic contribution to
ferroelectric polarization in undoped manganites, we evaluate the Berry phase
of orbital-polarizable Bloch electrons as an orbital ordering (OO) establishes
in the background of an antiferromagnetic E-type configuration. The onset of OO
is tuned by the Jahn-Teller (JT) interaction in a tight-binding model for
interacting electrons moving along zigzag chains. A finite polarization is
found as soon as the JT coupling is strong enough to induce OO, supporting the
large electronic contribution predicted from first principles.
