title: Phylogenetic relationships of graminicolous downy mildews based on cox2 sequence data.
abstract: Graminicolous downy mildews (GDM) are an understudied, yet economically important, group of plant pathogens, which are one of the major constraints to poaceous crops in the tropics and subtropics. Here we present a first molecular phylogeny based on cox2 sequences comprising all genera of the GDM currently accepted, with both lasting (Graminivora, Poakatesthia, and Viennotia) and evanescent (Peronosclerospora, Sclerophthora, and Sclerospora) sporangiophores. In addition, all other downy mildew genera currently accepted, as well as a representative sample of other oomycete taxa, have been included. It was shown that all genera of the GDM have had a long, independent evolutionary history, and that the delineation between Peronosclerospora and Sclerospora is correct. Sclerophthora was found to be a particularly divergent taxon nested within a paraphyletic Phytophthora, but without support. The results confirm that the placement of Peronosclerospora and Sclerospora in the Saprolegniomycetidae is incorrect. Sclerophthora is not closely related to Pachymetra of the family Verrucalvaceae, and also does not belong to the Saprolegniomycetidae, but shows close affinities to the Peronosporaceae. In addition, all GDM are interspersed throughout the Peronosporaceae s lat., suggesting that a separate family for the Sclerosporaceae might not be justified.
authors.affiliation: Universität Hohenheim, Institut für Botanik, Garbenstr. 30, 70599 Stuttgart, Germany. thines@uni-hohenheim.de
authors.forename: Marco
authors.initials: M
authors.lastname: Thines
authors.forename: Markus
authors.initials: M
authors.lastname: Göker
authors.forename: Sabine
authors.initials: S
authors.lastname: Telle
authors.forename: Malcolm
authors.initials: M
authors.lastname: Ryley
authors.forename: Kusum
authors.initials: K
authors.lastname: Mathur
authors.forename: Yaladabagi D
authors.initials: YD
authors.lastname: Narayana
authors.forename: Otmar
authors.initials: O
authors.lastname: Spring
authors.forename: Ram P
authors.initials: RP
authors.lastname: Thakur
mesh_terms: D020418:Algal Proteins / Q000737:chemistry / Q000235:genetics*; D001483:Base Sequence; D051546:Cyclooxygenase 2 / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D044742:Peronospora / Q000145:classification / Q000235:genetics*; D010802:Phylogeny; D010935:Plant Diseases / Q000382:microbiology; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: D020418:Algal Proteins; D051546:Cyclooxygenase 2