DsEcp2-1 is a polymorphic effector that restricts growth of Dothistroma septosporum in pine.

•Dothistroma septosporum (Ds) and Cladosporium fulvum share effector genes.•In Ds, many of these are pseudogenized or are poorly expressed in planta.•All these effectors are polymorphic among global Ds isolates.•DsEcp2-1 triggers cell death in a non-host plant and restricts Ds growth in pine.•These results suggest both pathogen and host adaptation at the molecular level.