Garibaldi A, Bertetti D, Gullino M L
Center of Competence AGROINNOVA, University of Torino, Via Leonardo da Vinci, 44, 10095 Grugliasco, Italy.
Plant Dis. 2009 Mar;93(3):320. doi: 10.1094/PDIS-93-3-0320C.
Cornus florida L. (Cornaceae), flowering dogwood, is a small deciduous tree whose showy inflorescences, clusters of bright red fruits and red and purple leaves in autumn, make it a much appreciated ornamental. During the summer of 2008, severe outbreaks of a previously unknown powdery mildew were observed in several gardens and nurseries in Piedmont (northern Italy). Young leaves were covered with dense, white mycelia and conidia, especially on the adaxial surface. As the disease progressed, infected leaves turned red. Conidia were hyaline, elliptical, borne singly, and measured 32 to 46 × 15 to 20 (average 38 × 17) μm. Conidiophores measured 68 to 77 × 8 to 9 (average 73 × 8) μm, with a cylindrical foot cell measuring 26 to 37 × 8 to 10 (average 31 × 9) μm, followed by two shorter cells. Fibrosin bodies were absent. No chasmothecia were observed. The ITS region (internal transcribed spacer) of rDNA was amplified using primers ITS4/ITS6 and sequenced. The 627-bp sequence (Accession No. EU FJ436989 in GenBank) has 99% identity with Erysiphe pulchra. As proof of pathogenicity, diseased leaves were pressed against leaves of three healthy 3-year-old plants. Three noninoculated plants served as controls. Inoculated and noninoculated plants were maintained outdoors at 13 to 21°C. After 15 days, typical powdery mildew colonies developed on inoculated plants. Noninoculated plants did not show symptoms. The pathogenicity test was carried out twice. To our knowledge, this is the first report of the presence of powdery mildew on C. florida caused by E. pulchra in Italy. Powdery mildew of dogwood, caused by Microsphaera (Erysiphe) pulchra, has been reported in the United States (3) and Japan (1). In Italy, a powdery mildew caused by an Oidium sp. has been reported on C. sanguinea (2). Herbarium specimens of this disease are available at AGROINNOVA Collection, University of Torino, Italy. References: (1) T. Kobayashi. Index of Fungi Inhabiting Woody Plants in Japan. Host, Distribution, and Literature. Zenkoku-Noson-Kyoikai Publishing Co., Ltd., Tokyo, 2007. (2) G. Sicoli et al. Inf. Agrario 56/48:84, 2000. (3) V. L. Smith. Plant Dis. 83:782, 1999.
多花梾木（山茱萸科），即花梾木，是一种小型落叶乔木，其艳丽的花序、成簇的鲜红色果实以及秋季的红紫色叶片使其成为备受喜爱的观赏植物。2008年夏季，在意大利北部皮埃蒙特的几个花园和苗圃中，观察到一种此前未知的白粉病严重爆发。幼叶上覆盖着密集的白色菌丝体和分生孢子，尤其是在叶片正面。随着病情发展，受感染的叶片变红。分生孢子无色透明，椭圆形，单生，大小为32至46×15至20（平均38×17）μm。分生孢子梗大小为68至77×8至9（平均73×8）μm，具一个圆柱形的基部细胞，大小为26至37×8至10（平均31×9）μm，其后跟着两个较短的细胞。无纤维状小体。未观察到闭囊壳。使用引物ITS4/ITS6扩增rDNA的ITS区域（内转录间隔区）并进行测序。该627 bp的序列（GenBank登录号为EU FJ436989）与美丽白粉菌有99%的同一性。作为致病性的证据，将患病叶片压在三株健康的3年生植株的叶片上。三株未接种的植株作为对照。接种和未接种的植株置于室外13至21°C环境中。15天后，接种植株上出现典型的白粉病菌落。未接种植株未表现出症状。致病性试验进行了两次。据我们所知，这是意大利首次报道由美丽白粉菌引起的多花梾木白粉病。由美丽小钩丝壳菌（美丽白粉菌）引起的梾木白粉病已在美国（3）和日本（1）有报道。在意大利，已报道了一种由粉孢属真菌引起的山茱萸白粉病（2）。这种病害的标本保存在意大利都灵大学的AGROINNOVA标本馆。参考文献：（1）T. Kobayashi。《日本木本植物上的真菌索引。寄主、分布及文献》。日本全国农村协会出版有限公司，东京，2007年。（2）G. Sicoli等人。《农业信息》56/48：84，2000年。（3）V. L. Smith。《植物病害》83：782，1999年。
