title: Re-consideration of Peronospora farinosa infecting Spinacia oleracea as distinct species, Peronospora effusa.
abstract: Downy mildew is probably the most widespread and potentially destructive global disease of spinach (Spinacia oleracea). The causal agent of downy mildew disease on various plants of Chenopodiaceae, including spinach, is regarded as a single species, Peronospora farinosa. In the present study, the ITS rDNA sequence and morphological data demonstrated that P. farinosa from S. oleracea is distinct from downy mildew of other chenopodiaceous hosts. Fifty-eight spinach specimens were collected or loaned from 17 countries of Asia, Europe, Oceania, North and South America, which all formed a distinct monophyletic group. No intercontinental genetic variation of the ITS rDNA within Peronospora accessions causing spinach downy mildew disease was found. Phylogenetic trees supported recognition of Peronospora from spinach as a separate species. Microscopic examination also revealed morphological differences between Peronospora specimens from Spinacia and P. farinosa s. lat. specimens from Atriplex, Bassia, Beta, and Chenopodium. Consequently, the name Peronospora effusa should be reinstated for the downy mildew fungus found on spinach. Here, a specimen of the original collections of Peronospora effusa is designated as lectotype.
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: Seung-Beom
authors.initials: SB
authors.lastname: Hong
authors.forename: Hyeon-Dong
authors.initials: HD
authors.lastname: Shin
mesh_terms: D000569:Americas; D001208:Asia; D004271:DNA, Fungal / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D005060:Europe; D044349:Oceania; D044742:Peronospora / Q000145:classification* / Q000166:cytology / Q000235:genetics; D010802:Phylogeny; D010935:Plant Diseases / Q000382:microbiology; D013045:Species Specificity; D018724:Spinacia oleracea / Q000382:microbiology*
chemical_list: D004271:DNA, Fungal; D004275:DNA, Ribosomal; D021903:DNA, Ribosomal Spacer