  We present a result which allows us to deform a Poisson-Nijenhuis manifold
into a Poisson quasi-Nijenhuis manifold by means of a closed 2-form. Under an
additional assumption, the deformed structure is also Poisson-Nijenhuis. We
apply this result to show that the canonical Poisson-Nijenhuis structure on
R^2n gives rise to both the Poisson-Nijenhuis structure of the open (or non
periodic) n-particle Toda lattice, introduced by Das and Okubo [6], and the
Poisson quasi-Nijenhuis structure of the closed (or periodic) n-particle Toda
lattice, described in our recent work [7].
