New Disease Reports
New Disease Reports (2008) 18, 2.
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First report of powdery mildew of Madagascar periwinkle caused by Eryisphe sp. in Japan

K. Watanabe 1* and Y. Sato 2

*wkyoko@agr.tamagawa.ac.jp

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Accepted: 18 Aug 2008

In May 2007, powdery mildew of Madagascar periwinkle (Catharanthus roseus) was observed on commercially grown plants (cv. Yellow Magic) at Kanagawa prefecture. Usually, the white powdery dusting of the fungus developed on the upper leaf surfaces, but it was also seen on the lower leaf surfaces. Symptoms sometimes included yellow and brown lesions (approximately 3-10 mm in diameter) in association with whitish masses of conidiophores and conidia (Fig. 1). For pathogenicity testing, conidia on the leaf surface of diseased plants were collected with a dry brush and transferred to each of five healthy leaves of C. roseus. These plants were kept at approximately 23°C and symptoms developed on one of the five leaves after 10 days.

Fungal morphology on the leaves was as follows: hyphae were branched and hyaline, lacking fibrosin bodies; conidiophores arose from the internal hyphae, and were septate, hyaline and cylindrical, 52-77 x 16-18 µm in diameter (Fig. 2); conidia were also hyaline and cylindrical, 35-45 x 13-20 µm in diameter, produced singly; and appressoria were of a simple lobed type (Fig. 3). These morphological characteristics corresponded to an anamorph stage of the genus Oidium, subgenus Pseudoidium, which belong to the genus Erysiphe.

For more specific identification by DNA analysis, the ITS 1-5.8S rDNA-ITS 2 region was amplified. The sequence (GenBank Accession No. AB355647) was most similar to that of Erysiphe elevata (AY587014: 99%). However, E. elevata is reported to be a pathogen of Bignoniaceae (Cook et al., 2006). Furthermore, we were unable to find chasmothecia on leaves of Madagascar periwinkle, and until a chasmothecium is found, this pathogen will be referred to as Erysiphe sp.

Powdery mildews on C. roseus have been recorded as Leveillula taurica in India and Korea (Amano, 1986; Shin 2000), and Oidium sp. in Tanzania and Venezuela (Amano, 1986). The reported powdery mildew of C. roseus is not endophytic and the conidiophore does not emerge through the stomata of the host. This feature is obviously different from that of L. taurica. This is the first record of powdery mildew caused by the genus Erysiphe of Madagascar periwinkle in Japan.

Figure1+
Figure 1: Powdery mildew on Madagascar periwinkle caused by Erysiphe sp. Symptoms included brown regions in association with white powdery masses.
Figure 1: Powdery mildew on Madagascar periwinkle caused by Erysiphe sp. Symptoms included brown regions in association with white powdery masses.
Figure2+
Figure 2: Conidiophore of Erysiphe sp. (Bar = 20 µm)
Figure 2: Conidiophore of Erysiphe sp. (Bar = 20 µm)
Figure3+
Figure 3: Mature conidium and appresorium of Erysiphe sp. (Bar = 20 µm)
Figure 3: Mature conidium and appresorium of Erysiphe sp. (Bar = 20 µm)

Acknowledgements

The authors would like to thank Prof. Dr. T. Hsiang, University of Guelph, for help in revising the manuscript.

References

  1. Amano K (Hirata), 1986. Host Range and Geographical Distribution of the Powdery Mildew Fungi. Tokyo, Japan: Science Society Press. 741 pp.
  2. Cook RTA, Henricot B, Henrici A, Beales P, 2006. Morphological and phylogenetic comparisons amongst powdery mildews on Catalpa in the UK. Mycological Research 110, 672-685.
  3. Shin, HD, 2000. Erysiphaceae of Korea. Suwon, Korea: National Institute of Agricultural Science and Technology. 320 pp.
This report was formally published in Plant Pathology

©2008 The Authors