  We show that, in local Calabi-Yau manifolds, the topological open string
partition function transforms as a wavefunction under modular transformations.
Our derivation is based on the topological recursion for matrix models, and it
generalizes in a natural way the known result for the closed topological string
sector. As an application, we derive results for vevs of 1/2 BPS Wilson loops
in ABJM theory at all genera in a strong coupling expansion, for various
representations.
