The oomycete pathogen Pseudoperonospora cubensis (Berk. and Curt.) Rostow. is a major foliar disease of cucumber (Cucumis sativus L.), especially in humid regions of the world (Palti and Cohen, 1980). Downy mildew was first described on cucumber by Berkeley and Curtis in 1868 and investigation into the genetic basis of resistance began in the early […]