First report of powdery mildew caused by Erysiphe betae on sugar beet in Korea

J. H. Joa, K. C. Seong, I. Y. Choi, S. E. Cho, H. D. Shin

Research output: Contribution to journalArticlepeer-review

Abstract

During the winter of 2015 and spring of 2016, sugar beet (Beta vulgaris L., Amaranthaceae) infected by a powdery mildew with about 20% disease incidence was found in a plastic greenhouse in Jeju (33°27′59″N, 126°31′14″E), Korea. Powdery mildew colonies first appeared as sparse white patches on both sides of the leaves. As the disease progressed, the plants were covered with abundant masses of conidia, resulting in reduced growth and premature senescence. A specimen was deposited in the Korea University Herbarium (accession KUS-F29140). Appressoria on hyphae were well-developed, multilobed or moderately lobed, and single or opposite in pairs. Conidiophores were straight, 75 to 120 × 6.5 to 9.5 µm. Foot-cells of conidiophores were cylindrical or slightly sinuous at the base, and 28 to 45 µm long. Conidia were cylindrical to oblong-elliptical, 35 to 50 × 13 to 18 µm with a length to width ratio of 2.0 to 2.8, showed angular to rectangular wrinkling of outer walls, and were lacking distinct fibrosin bodies. Germ tubes were produced in the perihilar position of conidia. No chasmothecia were found during the growing season. The fungal structures are typical of the powdery mildew Pseudoidium anamorph of the genus Erysiphe. The morphological characteristics and host range were consistent with those of E. betae (Vaňha) Weltzien (Braun and Cook 2012). To confirm the identification, the internal transcribed spacer (ITS) regions of isolate KUS-F29140 were amplified with primers ITS1/ITS4 and sequenced. The resulting 560 bp sequence was deposited in GenBank (accession KX574674). A GenBank BLAST search of the Korean isolate showed 100% identity with E. betae on sugar beet (DQ164432 and DQ164436). Pathogenicity was confirmed through inoculation by dusting conidia onto leaves of five healthy, potted sugar beets. Five noninoculated plants served as controls. Inoculated plants developed signs and symptoms of powdery mildew after 7 days, whereas the control plants remained symptomless. The fungus present on the inoculated plants was identical morphologically to that originally observed on diseased plants. Powdery mildew of sugar beet has been recorded worldwide wherever sugar beet is cultivated (Farr and Rossman 2016). To our knowledge, this is the first report of powdery mildew on sugar beet in Korea. Though sugar beet was once cultivated in the Pyongyang area (now North Korea) in the early 1900s (Nakata et al. 1924), there has been no commercial cultivation in Korea since that time. However, autumn-sowing and spring-harvesting of sugar beet as a winter crop in the Jeju area (southernmost island of Korea) has been attempted under organic farming practices in experimental farms (Loel and Hoffmann 2014; Son 1968). Routine field observations showed that there was no powdery mildew infection of sugar beet in open field production. Nevertheless, it might be a potential threat to open field production. Further monitoring and control strategies of sugar beet powdery mildew should be followed.

Original languageEnglish
Pages (from-to)254
Number of pages1
JournalPlant Disease
Volume101
Issue number1
DOIs
Publication statusPublished - 2017 Jan

ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Plant Science

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