title: Morphological and molecular characterization of the causal agent of downy mildew on Quinoa (Chenopodium quinoa).
abstract: Downy mildew is an economically important and widespread disease in quinoa (Chenopodium quinoa) growing areas. Although in many studies Peronospora farinosa is most commonly regarded as the causal agent of the disease, identification and classification of the pathogen remain still uncertain due to its taxonomic confusion. Thirty-six Peronospora isolates from quinoa with different geographic origins including Argentina, Bolivia, Denmark, Ecuador, and Peru were morphologically and molecularly compared with Peronospora species from other Chenopodium species. The morphology of three herbarium specimens was similar to that of P. variabilis, which originated from C. album, characterized by flexuous to curved ultimate branchlets and pedicellated conidia. Phylogenetic analysis based on ITS rDNA sequences also placed the quinoa pathogen within the same clade as P. variabilis. Within the ITS rDNA sequences of the quinoa pathogens, two base substitutions were found, which separated the majority of the Danish isolates from isolates from South America, but no sequence difference was found among the isolates from different cultivars of quinoa. The present results indicate that the pathogen responsible for the quinoa downy mildew is identical to Peronospora variabilis and that it should not be lumped with P. farinosa as claimed previously by most studies.
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: Solveig
authors.initials: S
authors.lastname: Danielsen
authors.forename: Mette
authors.initials: M
authors.lastname: Lübeck
authors.forename: Seung-Beom
authors.initials: SB
authors.lastname: Hong
authors.forename: Rolf
authors.initials: R
authors.lastname: Delhey
authors.forename: Hyeon-Dong
authors.initials: HD
authors.lastname: Shin
mesh_terms: D027465:Chenopodium quinoa / Q000382:microbiology*; D048028:DNA, Algal / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D003718:Denmark; D044742:Peronospora / Q000145:classification* / Q000166:cytology / Q000235:genetics; D010802:Phylogeny; D010935:Plant Diseases / Q000382:microbiology*; D013020:South America
chemical_list: D048028:DNA, Algal; D021903:DNA, Ribosomal Spacer