  We discuss infinite-dimensional hidden symmetry algebras (and hence an
infinite number of conserved nonlocal charges) of the N-extented self-dual
super Yang-Mills equations for general N\leq4 by using the supertwistor
correspondence. Furthermore, by enhancing the supertwistor space, we construct
the N-extended self-dual super Yang-Mills hierarchies, which describe infinite
sets of graded Abelian symmetries. We also show that the open topological
B-model with the enhanced supertwistor space as target manifold will describe
the hierarchies. Furthermore, these hierarchies will in turn -- by a
supersymmetric extension of Ward's conjecture -- reduce to the super
hierarchies of integrable models in D<4 dimensions.
