title: A molecular phylogeny of Phytophthora and related oomycetes.
abstract: Phylogenetic relationships among 50 Phytophthora species and between Phytophthora and other oomycetes were examined on the basis of the ITS sequences of genomic rDNA. Phytophthora grouped with Pythium, Peronospora, and Halophytophthora, distant from genera in the Saprolegniales. Albugo was intermediate between these two groups. Unlike Pythium, Phytophthora was essentially monophyletic, all but three species forming a cluster of eight clades. Two clades contained only species with nonpapillate sporangia. The other six clades included either papillate and semipapillate, or semipapillate and nonpapillate types, transcending traditional morphological groupings, which are evidently not natural assemblages. Peronospora was related to P. megakarya and P. palmivora and appears to be derived from a Phytophthora that has both lost the ability to produce zoospores and become an obligate biotroph. Three other Phytophthoras located some distance from the main Phytophthora-Peronospora cluster probably represent one or more additional genera.
authors.affiliation: Scottish Crop Research Institute, Invergowrie, Dundee, United Kingdom. d.cooke@scri.sari.ac.uk
authors.forename: D E
authors.initials: DE
authors.lastname: Cooke
authors.forename: A
authors.initials: A
authors.lastname: Drenth
authors.forename: J M
authors.initials: JM
authors.lastname: Duncan
authors.forename: G
authors.initials: G
authors.lastname: Wagels
authors.forename: C M
authors.initials: CM
authors.lastname: Brasier
mesh_terms: D004271:DNA, Fungal / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000235:genetics*; D019143:Evolution, Molecular; D008969:Molecular Sequence Data; D009868:Oomycetes / Q000145:classification / Q000235:genetics*; D010802:Phylogeny; D010838:Phytophthora / Q000145:classification / Q000235:genetics*; D010935:Plant Diseases / Q000382:microbiology; D016133:Polymerase Chain Reaction / Q000379:methods; D017422:Sequence Analysis, DNA
chemical_list: D004271:DNA, Fungal; D021903:DNA, Ribosomal Spacer