  It is known that the Kadomtsev-Petviashvili (KP) equation can be decomposed
into the first two members of the coupled Ablowitz-Kaup-Newell-Segur (AKNS)
hierarchy by the binary nonlinearization of Lax pairs. In this paper, we
construct the N-th iterated Darboux transformation (DT) for the second- and
third-order m-coupled AKNS systems. By using together the N-th iterated DT and
Cramer's rule, we find that the KPII equation has the unreduced multi-component
Wronskian solution and the KPI equation admits a reduced multi-component
Wronskian solution. In particular, based on the unreduced and reduced
two-component Wronskians, we obtain two families of fully-resonant line-soliton
solutions which contain arbitrary numbers of asymptotic solitons as
y->\mp\infty to the KPII equation, and the ordinary N-soliton solution to the
KPI equation. In addition, we find that the KPI line solitons propagating in
parallel can exhibit the bound state at the moment of collision.
