  We describe Scalar-Pseudoscalar partner degeneration at the QCD chiral
transition in terms of the dominant low-energy physical states for the light
quark sector. First, we obtain within model-independent one-loop Chiral
Perturbation Theory (ChPT) that the QCD pseudoscalar susceptibility is
proportional to the quark condensate at low $T$. Next, we show that this
chiral-restoring behaviour for $\chi_P$ is compatible with recent lattice
results for screening masses and gives rise to degeneration between the scalar
and pseudoscalar susceptibilities ($\chi_S$, $\chi_P$) around the transition
point, consistently with an O(4)-like current restoration pattern. This
scenario is clearly confirmed by lattice data when we compare $\chi_S(T)$ with
the quark condensate, expected to scale as $\chi_P(T)$. Finally, we show that
saturating $\chi_S$ with the $\sigma/f_0(500)$ broad resonance observed in pion
scattering and including its finite temperature dependence, allows to describe
the peak structure of $\chi_S(T)$ in lattice data and the associated critical
temperature. This is carried out within a unitarized ChPT scheme which
generates the resonant state dynamically and is also consistent with partner
degeneration.
