Plant Pathology (2004) 53, 527 Doi: 10.1111/j.1365-3059.2004.01019.x NEW DISEASE REPORT Blackwell Publishing, Ltd. First report of powdery mildew caused by Leveillula taurica on leek (Allium porrum) in Turkey S. Kurt*, S. Soylu, E. M. Soylu and F. M. Tok Department of Plant Protection, University of Mustafa Kemal, Faculty of Agriculture, 31034 Hatay, Turkey In the winter of 2002, typical symptoms of powdery mildew were observed on leek plants (Allium porrum) in the Arsuz district, located in the Mediterranean region of Turkey. Initially symptoms consisted of the extensive growth of a white, superficial powdery coating on the abaxial leaf surface. Newly infected leaves had a sparse covering of powdery mildew. As the disease progressed, white mycelial growth completely covered both leaf surfaces. Three weeks after initial observation, 71·7% of leeks were affected. The fungus produced mostly simple, straight, septate conidiophores (300– 400 × 5–7 µ m) arising from endophytic mycelium through stomata. Hyaline, single-celled primary and secondary conidia were borne on conidiophores. Primary conidia were lanceolate with distinct apical points, 57·3–79·6 µm × 14·2–18·5 µm. Secondary conidia were cylindrical to long, obovate with rounded ends, 55·9–80·3 µm × 12·0–15·3 µm. Globose, spherical, dark brown chasmothecia were scattered to occasionally gregarious, 160 –210 µm in diameter, immersed in a dense mass of mycelium. Unbranched appendages were light to dark brown (4 –7 µm in diameter). Each chasmothecium contained 12– 45 two-spored, stalked asci (75–98 × 18 – 32 µm). Ascospores were ellipsoid to ovoid, 37–40 × 15 – 18 µm in diameter. Pathogenicity tests were performed by dusting conidia from naturally infected leek leaves onto water-misted abaxial leaf surface of 40-day-old healthy leek seedlings (cv. Uzun Bacak). Plants were enclosed in polyethylene bags for 2 days at 25°C and 80% relative humidity (RH), before being moved into a growth chamber at 25 ± 2°C, 75% RH with a 16 h photoperiod. Symptoms identical to that of naturally infected plants became visible 3 – 4 weeks after inoculation. No symptoms developed on control plants. Based on the occurrence of the disease, the presence of endophytic mycelium, characteristics of asexual and teleomorph stages (Braun, 1987; Palti, 1988), the pathogen was identified as Leveillula taurica. To our knowledge, this is the first report of Leveillula taurica on leek in Turkey. Powdery mildew infection on leeks and several other species, including onion, garlic, carrot and fennel, have been previously reported in northern Italy and Korea (Gullino et al., 1989; Shin, 2000). References Braun U, 1987. A monograph of the Erysiphales (powdery mildews). Beiheft zur Nova Hedwigia 89, 1–700. Gullino ML, Lento G, Garibaldi A, 1989. Purple blotch and powdery mildew: two new diseases of leek in Liguria. Difesa-Delle-Piante 12, 1–2. Palti J, 1988. The Leveillula mildews. Botanical Review 54, 423–535. Shin HD, 2000. Erysiphaceae of Korea. Suwon, South Korea: National Institute of Agricultural Science and Technology. *E-mail: senerk31040@yahoo.com Accepted 6 January 2004 at www.bspp.org.uk/ndr where figures relating to this paper can be viewed © 2004 BSPP 527