  We analyze the relation between the present (and foreseen) bounds on matter
stability and the presence of TeV-scale color octet scalar states in
nonsupersymmetric SO(10) grand unification with one adjoint Higgs
representation triggering the symmetry breaking. This scenario, discarded long
ago due to tree-level tachyonic instabilities appearing in all
phenomenologically viable breaking patterns, has been recently revived at the
quantum level. By including the relevant two-loop corrections we find a tight
correlation between the octet mass and the unification scale which either
requires a light color octet scalar within the reach of the LHC or,
alternatively, a proton lifetime accessible to the forthcoming megaton-scale
facilities.
