Scalar-isoscalar states (0++) are investigated within the large-Nc Regge
approach. We elaborate on the consequences of including the lightest f0(600)
scalar-isoscalar state into such an analysis, where the position of f0(600)
fits very well into the pattern of the radial Regge trajectory. Furthermore, we
point out that the pion and nucleon spin-0 gravitational form factors, recently
measured on the lattice, provide valuable information on the low-mass spectrum
of the scalar-isoscalar states on the basis of the scalar-meson dominance in
the spin-0 channel. Through the fits to these data we find m_sigma= 450-600
MeV. We compare the predictions of various fits and methods. An analysis of the
QCD condensates in the two-point correlators provides further constraints on
the parameters of the scalar-isoscalar sector. We find that a simple two-state
model suggests a meson nature of f0(600), and a glueball nature of f0(980),
which naturally explains the ratios of various coupling constants. Finally, we
note that the fine-tuned condition of the vanishing dimension-2 condensate in
the Regge approach with infinitely many scalar-isoscalar states yields a
reasonable value for the mass of the lighest glueball state.Comment: 18 pages, 13 figures. Typos corrected. Remarks and references adde