  In the light pseudoscalar sector, we study rooted staggered chiral
perturbation theory in the two-flavor case. The pion mass and decay constant
are calculated through NLO for a partially-quenched theory. In the limit where
the strange quark mass is large compared to the light quark masses and the
taste splittings, we show that the SU(2) staggered chiral theory emerges from
the SU(3) staggered chiral theory, as expected. Explicit relations between
SU(2) and SU(3) low energy constants and taste-violating parameters are given.
A brief summary of updated SU(2) chiral fits to the MILC lattice data is
presented.
