  The worldline representation of the one loop fermionic effective action is
used to obtain the vertex operator for the pion and the sigma in QCD strings.
The vertex operator of the scalar sigma is distinguished from that of the
pseudo-scalar pion by the presence of an additional operator m V_{0} where m is
the current quark mass and V_{0} is a vertex operator that would describe a
tachyon in the open bosonic string theory. This leads to a relation between the
sigma propagator and the pion propagator, when chiral symmetry is spontaneously
broken this relation implies that the propagator constructed from V_{0} must
behave like a massless ghost state. The presence of this state ensures that the
sigma is massive and no longer degenerate with the pion. The expectation value
of V_{0} in a string description is related to the vacuum expectation value of
the chiral condensate in QCD. Our analysis emphasizes the need for boundary
fermions in any string representation of mesons and is suggestive of world
sheet supersymmetry.
