  We deduce the gluino contribution to the three-loop QCD \beta function within
the minimal supersymmetric Standard Model (MSSM) from its standard QCD
expression. The result is a first step in the computation of the full MSSM
three-loop \beta function. In addition, in the case of a light gluino it
provides the strong three-loop SUSY correction to the extrapolation of the
strong coupling constant from the low energy regime to the Z region and up to
the squark threshold.
