Phytophthora x pelgrandis, a new natural hybrid pathogenic to Pelargonium grandiflorum hort.

A new Phytophthora hybrid of Ph. cactorum (Leb. & Cohn) Schroet. and Ph. nicotianaevan Breda de Haan pathogenic to cultivars of Pelargonium grandiflorum hort. is described as Phytophthora X pelgrandis and its morphological features are documented. Morphological, physiological (e.g., temperature requirements) and molecular data (DNA sequencing, random amplified polymorphic DNA-PCR) are presented for isolates of the Phytophthora hybrid. Pathogenicity was tested on cultivars of P. grandiflorum and Nicotiana tabacum. For comparison cultures of the parental species and additional Phytophthora taxa also were examined.