First report of powdery mildew caused by Neoerysiphe galeopsidis on Stachys affinis in Korea

I. Y. Choi, J. H. Kim, K. M. Kim, S. E. Cho, H. D. Shin

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Stachys affinis Bunge, known as Chinese artichoke, is native to northern China and is widely distributed in Asia, North America, and Europe. Its tuberous roots are used for medicinal purposes (Hayashi et al. 1994). In September 2014, powdery mildew was observed on hundreds of S. affinis plants grown in semi-shady areas on a farm near Iksan City, Korea, at approximately 50% disease incidence. Negligible disease was observed on nearby farms on unshaded crops. Symptoms first appeared as thin white colonies, which subsequently developed into abundant hyphal growth on stems and both sides of the leaves. Voucher specimens were deposited in the Korea University Herbarium (KUS). Appressoria were moderately lobed to multilobed. Conidiophores were 114 to 200 × 9 to 11 μm and produced 2 to 6 immature conidia in chains with a sinuate outline, followed by 1 to 3 straight cells. Foot-cells of conidiophores were straight, cylindrical, and 30 to 50 μm long. Conidia were hyaline, cylindric oval to ellipsoid, 28 to 38 × 15 to 20 μm (length/width ratio = 1.7 to 2.2), and devoid of conspicuous fibrosin bodies. Germ tubes were produced on the perihilar or lateral position of conidia. Dark brown chasmothecia were spherical, 110 to 150 µm in diameter, and contained 6 to 10 asci. Appendages numbering 10 to 30 per chasmothecium were mycelioid, 0.5 to 2.5 times as long as the chasmothecial diameter, and brown at the base and becoming paler toward the tip. Asci were broadly ellipsoid-ovoid, stalked, and 45 to 65 × 20 to 30 μm. No mature ascospores were found. Measurements and morphological characteristics were consistent with those of Neoerysiphe galeopsidis (DC.) U. Braun (Braun and Cook 2012). To confirm the identification, molecular analysis of internal transcribed spacer (ITS) regions of ribosomal DNA (rDNA) sequence of KUS-F28368 was performed. The complete ITS regions of rDNA were amplified using primers ITS1/ITS4, and sequenced. The resulting 691-bp sequence was deposited in GenBank (Accession No. KR261582). A GenBank BLAST search using the Korean isolate showed >99% similarity with N. galeopsidis isolate from S. palustris (AB329679 from Switzerland) and lamiaceous hosts (e.g., AB498940, AB498945, and AB498946). Pathogenicity was confirmed by dusting conidia onto five leaves of a potted plant. Five noninoculated leaves of another potted plant served as controls. Powdery mildew developed on all inoculated leaves after 5 to 7 days. Noninoculated plants did not develop powdery mildew. Pathogenicity test was repeated twice with similar results. Previously, the powdery mildew infections associated with S. affinis have only been recorded as Oidium spp. from Japan (Amano 1986; Farr and Rossman 2015). To our knowledge, this is the first report of powdery mildew caused by N. galeopsidis on S. affinis in Korea. Although powdery mildew occurred primarily on crops grown in shaded areas, the disease poses a new threat to production of this medicinal crop. Further work is needed to examine the effect of light intensity on the severity of this disease.

Original languageEnglish
Pages (from-to)218
Number of pages1
JournalPlant Disease
Issue number1
Publication statusPublished - 2016 Jan 1

Bibliographical note

Publisher Copyright:
© The American Phytopathological Society.

ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Plant Science


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