First report of powdery mildew caused by podosphaera astericola on aster Glehnii in Korea

S. E. Cho, J. H. Park, I. Y. Choi, Y. J. Choi, H. D. Shin

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Aster glehnii F. Schmidt is a perennial plant in family Asteraceae and is distributed in the Russian Far East, Japan, and Korea. Extract from whole plant bodies has been used traditionally in Asian folk medicine for anti-inflammation activity and recently as an ingredient for cosmetic formulations (Kim et al. 2010). In Korea, young leaves and stems of A. glehnii, collected from the wild, have long been used as vegetables. In October 2015, dozens of A. glehnii plants showing symptoms of powdery mildew were observed in a public garden (35°48′06.5″ N; 128°31′14.2″ E) of Daegu City, Korea. The powdery mildew colonies were circular to irregular, forming thin white patches on both sides of the leaves. A representative specimen was deposited in the Korea University Herbarium (KUS-F28898). Hyphae were flexuous to straight, branched, septate, and 4 to 7 μm wide. Hyphal appressoria were nipple-shaped or nearly absent. Conidiophores were straight, 130 to 230 × 10 to 12 μm and produced 2 to 5 immature conidia in chains with a crenate outline. Foot-cells of conidiophores were cylindric, 38 to 65 μm long, and somewhat constricted at the basal septum. Conidia were ellipsoid-ovoid to barrel-shaped, measured 28 to 38 × 17 to 23 μm with a length/width ratio of 1.4 to 2.1, and had distinct fibrosin bodies. Germ tubes were produced from the lateral position of conidia. No chasmothecia were found. These structures are typical of the powdery mildew Euoidium anamorph of the genus Podosphaera. Morphological characteristics and host range were consistent with those of P. astericola U. Braun & S. Takam. (Braun and Cook 2012). To confirm the identification, the complete internal transcribed spacer (ITS) region of rDNA of isolate KUS-F28898 was amplified and sequenced with the primers ITS5 and P3 as described by Takamatsu et al. (2009). The resulting 585-bp sequence was deposited in GenBank (Accession No. KU147187). A BLAST search of the Korean isolate showed >99% similarity with those of P. astericola isolates on asteraceous hosts from Japan (AB040335, AB040341, and AB040353). Pathogenicity was confirmed by dusting the conidia from a diseased leaf onto young leaves of three healthy plants. Three noninoculated plants were used as negative controls. Inoculated leaves developed symptoms after 7 days, whereas the control plants remained symptomless. The fungus present on the inoculated plants was morphologically identical to that originally observed on diseased plants. Though several species of Aster have been known to be infected with P. astericola (Meeboon and Takamatsu 2015), A. glehnii was known to be infected with P. xanthii in Japan (Tanda et al. 1995; Braun and Cook 2012). To our knowledge, this is the first report of powdery mildew caused by P. astericola on A. glehnii globally as well as in Korea. Since this plant was commercially developed as edible greens and is cultivated under organic farming in Korea, occurrence of powdery mildew might be a potential threat to cost effective production of this plant.

Original languageEnglish
Pages (from-to)1017
Number of pages1
JournalPlant Disease
Issue number5
Publication statusPublished - 2016 May

ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Plant Science


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