  The validity of SU(4)-flavor symmetry relations of couplings of charmed $D$
mesons to light mesons and baryons is examined with the use of $^3{\rm P}_0$
quark-pair creation model and nonrelativistic quark model wave functions. We
focus on the three-meson couplings $\pi\pi\rho$, $KK\rho$ and $DD\rho$ and
baryon-baryon-meson couplings $NN\pi$, $N\Lambda K$ and $N\Lambda_c D$. It is
found that SU(4)-flavor symmetry is broken at the level of 30% in the $DD\rho$
tree-meson couplings and 20% in the baryon-baryon-meson couplings. Consequences
of these findings for DN cross sections and existence of bound states D-mesons
in nuclei are discussed.
