Refinements of the bottom and strange MSSM Higgs Yukawa couplings at NNLO

We extend the already existing two-loop calculation of the effective bottom-Yukawa coupling in the MSSM. In addition to the resummation of the dominant corrections for large values of tgβ, we include the subleading terms related to the trilinear Higgs coupling A$_{b}$ and contributions induced by the electroweak gauge couplings. This calculation has been extended to the NNLO corrections to the MSSM strange-Yukawa coupling. Our analysis leads to residual theoretical uncertainties of the effective Yukawa couplings at the per-cent level.