  Filling-control metal-insulator transitions (MITs) and related electronic
phase diagrams have been investigated for hole-doped vanadium oxides,
Pr_{1-x}Ca_xVO_3, Nd_{1-x}Sr_xVO_3 and Y_{1-x}Ca_xVO_3, with perovskite
structure. The increase of the doping level x causes the melting of the G-type
(and C-type) orbital order, prior to or concomitantly with the MIT, due partly
to the doped-hole motion and partly to the ramdom potential arising from the
quenched disorder. In particular, the G-type spin- and C-type orbital-ordered
phase present in Y_{1-x}Ca_xVO_3 disappears immediately upon hole doping,
around x=0.02. On the other hand, the critical doping level x for MIT is
governed by the electron-correlation strength of the undoped parent compound.
