First report of powdery mildew caused by golovinomyces cichoracearum on Tragopogon dubius in Korea

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

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Tragopogon dubius Scop., known as western salsify, is native to southern and central Europe and western Asia, but currently is a notorious invasive plant in many countries, including in North America. This plant was widely naturalized and has been disturbing native plant communities in Korea after being introduced accidentally in the early 1990s (Park 1999). In July 2015, dozens of plants exhibiting powdery mildew symptoms were found in Daegu (35°50′21.4″ N; 128°27′56.6″ E), Korea. Powdery mildew colonies first appeared as thin, white patches, but soon progressed to abundant hyphal growth on both sides of the leaves and stems. Severe infections caused leaf withering and premature senescence. Three voucher specimens were deposited in the Korea University Herbarium (KUS F28770, F28790, and F28801). Appressoria on the mycelium were lobed. Conidiophores measured 90 to 170 × 10 to 12 μm, were arising laterally from hyphal mother cells, and produced 2 to 5 immature conidia in chains with a sinuate outline, followed by 2 to 3 cells. Foot-cells of the conidiophores were 40 to 75 μm long and characterized by a distinctly curved base. Conidia were ellipsoid to barrel-shaped, 30 to 40 × 14 to 20 μm (length/width ratio of 1.5 to 2.5), lacked distinct fibrosin bodies, and showed reticulate wrinkling of the outer walls. Germ tubes were produced on the perihilar position of conidia. No chasmothecia were observed. These features were typical of the powdery mildew Euoidiumanamorph of the genus Golovinomyces. Lobed appressoria and curved foot-cells of the Korean specimens are consistent with G. cichoracearum (DC.) V.P. Heluta, originated from some asteraceous plants (e.g., Lactuca, Scorzonera, Tragopogon) (Braun and Cook 2012). To confirm the tentative identification, the complete internal transcribed spacer (ITS) region of rDNA was amplified and sequenced for KUS-F28801, with primers ITS1/ITS4 (White et al. 1990). The resulting 467-bp sequence was deposited in GenBank (Accession No. KU232994). The ITS sequence shared >99% similarity with G. cichoracearum on T. pratensis from Lithuania (AB769449), T. buphthalmoidesfrom Iran (AB077694), and Scorzonera hispanica from Lithuania (AB077682) and Germany (GQ183946). Pathogenicity was confirmed through artificial inoculation by gently dusting conidia onto healthy leaves of five potted plants. Five noninoculated plants served as controls. Inoculated plants developed symptoms after 5 days, whereas the control plants remained symptomless. The fungus present on the inoculated plants was identical morphologically to that originally observed on diseased plants. Associations of T. dubius and Golovinomyces have been reported in Europe (Farr and Rossman 2015). To our knowledge, this is the first report of powdery mildew caused by G. cichoracearum on T. dubius in Korea. The field observations suggest powdery mildew could limit expansion of this invasive weed in Korea.

Original languageEnglish
Pages (from-to)1496
Number of pages1
JournalPlant Disease
Issue number7
Publication statusPublished - 2016 Jul

ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Plant Science


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