On linear operators with p-nuclear adjoints

If $p\in [1,+\infty]$ and $T$ is a linear operator with $p$-nuclear adjoint from a Banach space $X$ to a Banach space $Y$ then if one of the spaces $X^*$ or $Y^{***}$ has the approximation property, then $T$ belongs to the ideal $N^p$ of operators which can be factored through diagonal oparators $l_{p'}\to l_1.$ On the other hand, there is a Banach space $W$ such that $W^{**}$ has a basis and such that for each $p\in [1,+\infty], p\neq 2,$ there exists an operator $T: W^{**}\to W$ with $p$-nuclear adjoint that is not in the ideal $N^p,$ as an operator from $W^{**}$ to $W.$