  We summarize the different features of the scalar mesons from QCD spectral
sum rule analyses of the two- and three-point functions. The results do not
favour the u-bar u + d-bar d interpretation of the broad and low mass sigma
(0.6), and the u-bar s resonance nature of the eventually observed kappa(0.9)
meson. We also discuss some OZI-violating and classic semileptonic and
radiative decay processes which can reveal in a model-independent way the
eventual gluon component sigma_B of the sigma. In a meson-gluonium mixing
scenario, one also expects an observation of the K K-bar final states from the
sigma_B which may compete (if phase space allowed) with the one from a low mass
s-bar s state assumed in the literature to be the SU(3) partner of the $\sigma
(0.6)$ if this latter is a u-bar u + d-bar d state
