title: Morphological and molecular analyses support the existence of host-specific Peronospora species infecting Chenopodium.
abstract: About 20 species of Peronospora have been reported to cause downy mildew on Chenopodium, but, particularly in plant pathology literature, only one species, P. farinosa, is considered to be involved. We performed sequence analysis of the ITS rDNA to reveal the phylogenetic relationships of Peronospora specimens from five species of Chenopodium, viz. C. album, C. ambrosioides, C. bonus-henricus, C. hybridum, and C. polyspermum. The five clades corresponded to particular Chenopodium species, and showed a high level of sequence divergence. Differences in the morphology of the conidia and ultimate branchlets also supported the separation of the five groups at the host species level. These results suggest that the names P. variabilis, P. boni-henrici, P. chenopodii, and P. chenopodii-polyspermi should be used for the four downy mildew pathogens specific to C. album, C. bonus-henricus, C. hybridum, and C. polyspermum, respectively. The Peronospora on C. ambrosioides was found to be an independent species.
authors.affiliation: Division of Environmental Science and Ecological Engineering, College of Life Sciences and Biotechnology, Korea University, Seoul, 136-701, Korea.
authors.forename: Young-Joon
authors.initials: YJ
authors.lastname: Choi
authors.forename: Cvetomir M
authors.initials: CM
authors.lastname: Denchev
authors.forename: Hyeon-Dong
authors.initials: HD
authors.lastname: Shin
mesh_terms: D027462:Chenopodium / Q000382:microbiology*; D016000:Cluster Analysis; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000737:chemistry / Q000235:genetics; D044742:Peronospora / Q000145:classification* / Q000166:cytology / Q000235:genetics / Q000302:isolation & purification*; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D013172:Spores, Fungal / Q000166:cytology
chemical_list: D004271:DNA, Fungal; D021903:DNA, Ribosomal Spacer