  The asymmetry of $D^-$ and $D^+$ meson production in $\pi^-N$ scattering
observed by the E791 experiment is a typical phenomenon known as the leading
particle effect in charm hadroproducton. We show that the phenomenon can be
explained by the effect of light quark fragmentation into charmed hadrons
(LQF). Meanwhile, the size of the LQF effect is estimated from data of the E791
experiment.
  A comparison is made with the estimate of the LQF effect from prompt
like-sign dimuon rate in neutrino experiments. The influence of the LQF effect
on the measurement of nucleon strange distribution asymmetry from charged
current charm production processes is briefly discussed.
