A   form   of  corrections  to  the  linear
trajectories on the plane m^2(n) (m is the mass
of  the  n-th radial excitation) for vector and
scalar  mesons is found that meets the operator
product   expansion   for   the   corresponding
two-point    correlators    and    the   hadron
phenomenology.  Methods of treatment the planar
QCD   sum   rules   at   calculating   physical
quantities  and  matching  to  effective  field
theory  is  worked  out systematically. A broad
symmetry   in   spectra   of  light  mesons  is
discovered.  Based  on  this  symmetry,  a  new
classification   for  light  mesons  explaining
their   masses   is   proposed.   A   class  of
holographic  models  is  built  that  describes
finite  number of states possessing approximate
Regge  spectrum  and  merging  resonances  into
continuum.  It  is  proven that the holographic
models of QCD in their application to the meson
spectroscopy     represent    a    mathematical
reformulation  of QCD sum rules in the limit of
large   number   of   colors.   A   method  for
constructing  effective five-dimensional models
is worked out that describes dynamics of strong
interactions  at  low and intermediate energies
and  is alternative to the standard holographic
approach.