  Various models of quantum gravity imply the Planck-scale modifications of
Heisenberg's uncertainty principle into a so-called generalized uncertainty
principle (GUP). The GUP effects on high-energy physics, cosmology, and
astrophysics have been extensively studied. Here, we focus on the
weak-equivalence-principle (WEP) violation induced by the GUP. Results from the
WEP test with the $^{85}$Rb-$^{87}$Rb dual-species atom interferometer are used
to set upper bounds on parameters in two GUP proposals. A $10^{45}$-level bound
on the Kempf-Mangano-Mann proposal, and a $10^{27}$-level bound on Maggiore's
proposal, which are consistent with bounds from other experiments, are
obtained. All these bounds have huge room for improvement in the future.
