  Flavor mixing in the quark-squark-gluino coupling is studied for the minimal
SU(5) SUGRA-GUT model and applied to evaluation of the nucleon lifetime. All
off-diagonal (generation mixing) elements of Yukawa coupling matrices and of
squark/slepton mass matrices are included in solving numerically one-loop
renormalization group equations for MSSM parameters, and the parameter region
consistent with the radiative electroweak symmetry breaking condition is
searched. It is shown that the flavor mixing in the gluino coupling for a large
$\tan\beta$ is of the same order of magnitude as the corresponding
Kobayashi-Maskawa matrix element in both up-type and down-type sector. There
exist parameter regions where the nucleon decay amplitudes for charged lepton
modes are dominated by the gluino dressing process, while for all the examined
regions the neutrino mode amplitudes are dominated by the wino dressing over
the gluino dressing.
