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© 2004 Plant Management Network.
Accepted for publication 10 November 2004. Published 8 December 2004.


First Report of Powdery Mildew of Lycium chinense (Chinese Matrimony Vine) Caused by Arthrocladiella mougeotii in the Pacific Northwest


Dean A. Glawe, Plant Pathologist, Puyallup Research and Extension Center, Washington State University, 7612 Pioneer Way East, Puyallup 98371-4998


Corresponding author: Dean A. Glawe. glawe@wsu.edu


Glawe, D. A. 2004. First report of powdery mildew of Lycium chinense (Chinese matrimony vine) caused by Arthrocladiella mougeotii in the Pacific Northwest. Online. Plant Health Progress doi:10.1094/PHP-2004-1208-01-HN.


Lycium chinense Mill. (Chinese matrimony-vine) (Solanaceae) is a traditional medicinal plant grown in China (4) and used as a perennial landscape plant in North America. During the 2002-2004 growing seasons, two specimen plants of L. chinense in the Medicinal Herb Garden at the University of Washington, Seattle exhibited conspicuous symptoms and signs of powdery mildew. This report documents the presence of powdery mildew on L. chinense in the Pacific Northwest and describes and illustrates morphological features of the causal agent, determined to be Arthrocladiella mougeotii (Lév.) Vassilkov. This appears to be the first report of a powdery mildew caused by Arthrocladiella in the Pacific Northwest.

Signs of the disease (Fig. 1) included effuse to dense patches of white to grayish mycelia on leaf surfaces and stems. Infected leaves frequently exhibited chlorotic mottling. The fungus formed superficial hyphae with nipple-shaped appressoria (Fig. 2); conidiophore (Fig. 3) foot cells that were cylindrical and measured (18-) 24-34 (-46) × (5.5-) 8.5-10.5 (-11.5) µm; and conidia (Fig. 4) that were ovoid to short-cylindrical, lacked fibrosin bodies, measured (18.5-) 23-30 (-31.5) × (10-) 11-15 (-15.5) µm and formed in chains. (Please note that size ranges follow standard mycological usage [e.g., 2], where the typical range is nested within the observed extreme values which are given in parentheses). The teleomorph was not observed. A voucher specimen was deposited with the Mycological Herbarium of the Department of Plant Pathology at Washington State University.


     
 

Fig. 1. Symptoms and signs of powdery mildew of L. chinense.

 

Fig. 2. Appressorium formed by A. mougeotii on L. chinense (differential interference contrast microscopy).

 

     
 

Fig. 3. Conidiophore, adjacent to two detached conidia, formed by A. mougeotii on L. chinense (brightfield microscopy).

 

Fig. 4. Conidium formed by A. mougeotii on L. chinense (differential interference contrast microscopy).

 

Fungal morphological features and the host matched the features characteristic of A. mougeotii (2). In particular, the nipple-shaped appressoria, lack of fibrosin bodies, and chains of ovoid to short-cylindrical conidia formed on L. chinense distinguish the fungus from other powdery mildews (1,2,3). Ascocarps were lacking in the multiple collections made from the two diseased plants during 2002-2004, consistent with the observations of Braun (2,3) and Bosewinkel (1) that A. mougeotii seldom forms the sexual state. There seems to be some disagreement as to whether A. mougeotii is the only powdery mildew species attacking Lycium species. Bosewinkel (1) listed two other species from Lycium species, both readily differentiated from A. moutgeotii on the basis of features of the anamorphs. He (1) distinguished Microsphaera diffiusa Cooke & Peck on the basis of lobed appressoria, and Sphaerotheca pannosa (Wall.: Schlecht) Lév. on the basis of fibrosin bodies. Braun (2,3) listed only A. mougeotii, the sole species of Arthrocladiella, as occurring on this host genus.

Although the observed diseased plants were visually unappealing, they grew vigorously each year and seemed able to tolerate the presence of the disease. At present it is unclear how the fungus survives the winter. There are no reports of A. mougeotii occurring on genera other than Lycium so it is unlikely that other Solanaceae (or species from other host families) serve as a source of inoculum. Given the relatively mild climate of western Washington, it is possible that the fungus persists through the winter months in the form of mycelium on infected plants. This possibility is consistent with the observation that the two specimen plants studied exhibited symptoms in each of three consecutive years.


Literature Cited

1. Bosewinkel, H. J. 1980. A note on the classification of Microsphaera mougeotii Lév. Cryptog. Mycol. 1:105-110.

2. Braun, U. 1987. A monograph of the Erysiphales (powdery mildews). Beih. Nova Hedwigia 89:1-700.

3. Braun, U. 1995. The powdery mildews of Europe. Gustav Fischer Verlag, Jena.

4. Bremness, L. 1994. Herbs. Dorling Kindersley, London.