We discuss the low energy effective action of QCD in the quark sector. When
it is built at the CSB (chiral symmetry breaking) scale by means of
perturbation theory it has the structure of a generalized Nambu-Jona-Lasinio
(NJL) model with CSB due to attractive forces in the scalar channel. We show
that if the lowest scalar meson state is sufficiently lighter than the heavy
pseudoscalar π′ then QCD favors a low-energy effective theory in which
higher dimensional operators (of the Nambu-Jona-Lasinio type) are dominated and
relatively strong. A light scalar quarkonium (mσ​=500÷600 MeV)
would provide an evidence in favor to this NJL mechanism. Thus the non-chiral
Quasilocal Quark Models (QQM) in the dynamical symmetry-breaking regime are
considered as approximants for low-energy action of QCD. In the mean-field
(large-N_c) approach the equation on critical coupling surface is derived. The
mass spectrum of scalar and pseudoscalar excited states is calculated in
leading-log approach which is compatible with the truncation of the QCD
effective action with few higher-dimensional operators. The matching to QCD
based on the Chiral Symmetry Restoration sum rules is performed and it helps to
select out the relevant pattern of CSB as well as to enhance considerably the
predictability of this approach.Comment: 10 pages, Latex, talk at the Workshop HADRON 99, Coimbra, Portuga