Garibaldi A, Bertetti D, Gullino M L
Centre of Competence AGROINNOVA, University of Torino, Via Leonardo da Vinci 44, 10095 Grugliasco, Italy.
Plant Dis. 2007 Sep;91(9):1203. doi: 10.1094/PDIS-91-9-1203C.
Coreopsis lanceolata L. (Asteraceae) is an ornamental species grown in parks and gardens and very much appreciated for its long-lasting flowering period. During the summer and fall of 2006, severe outbreaks of a previously unknown powdery mildew were observed on plants in several gardens near Biella (northern Italy). Both surfaces of leaves of the affected plants were covered with dense white mycelia and conidia. As the disease progressed, infected leaves turned yellow and died. Mycelia and conidia also were observed on stems and flower calyxes. Conidia were hyaline, ellipsoid, borne in short chains (5 to 6 conidia per chain) and measured 33 × 20 (27 to 35 × 17 to 22) μm. Conidiophores, 68 × 11 (62 to 76 × 10 to 12) μm, showed the foot cell measuring 50 × 11 (38 to 58 × 10 to 12) μm, followed by one shorter cell measuring 18 × 12 (13 to 19 × 12 to 13) μm. Fibrosin bodies were present. Chasmothecia were spherical and amber with a diameter of 99 (93 to 105) μm. Each chasmothecium contained one ascus with eight ascospores. On the basis of its morphology, the causal agent was determined to be a Podosphaera sp. (1). The ITS region (internal transcribed spacer) of rDNA was amplified using primers ITS4/ITS6 and sequenced. BLASTn analysis (1) of the 531 bp obtained showed an E-value of 0.0 with Podosphaera fusca (3). The nucleotide sequence has been assigned GenBank Accession No. EF 442023. Pathogenicity was confirmed through inoculations by gently pressing diseased leaves onto leaves of healthy C. lanceolata plants. Three plants were inoculated. Three noninoculated plants served as the control. Plants were maintained in a greenhouse at temperatures ranging from 20 to 28°C. Twelve days after inoculation, typical symptoms of powdery mildew 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 powdery mildew on C. lanceolata in Italy. Species of Coreopsis were previously described as host to Erysiphe cichoracearum, Sphaerotheca macularis and Leveillula taurica and S. fusca (2,4). Voucher specimens are available at the AGROINNOVA Collection, University of Torino. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) U. Braun. A Monograph of the Erysiphaceae (Powdery Mildews). Cramer, Berlin, GDR, 1987. (3) U. Braun and S. Takamatsu. Schlechtendalia 4:1, 2000 (4) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society. St Paul, MN, 1989.
柳叶金鸡菊（菊科）是一种种植于公园和花园的观赏植物，因其花期持久而备受喜爱。2006年夏秋时节，在比耶拉（意大利北部）附近的几个花园中，人们观察到一种此前未知的白粉病在植物上严重爆发。受感染植株的叶片两面都布满了密集的白色菌丝体和分生孢子。随着病情发展，受感染的叶片变黄并死亡。在茎和花萼上也观察到了菌丝体和分生孢子。分生孢子透明，椭圆形，呈短链状（每条链有5至6个分生孢子），大小为33×20（27至35×17至22）μm。分生孢子梗大小为68×11（62至76×10至12）μm，基部细胞大小为50×11（38至58×10至12）μm，其后是一个较短的细胞，大小为18×12（13至19×12至13）μm。有纤维状小体。闭囊壳球形，琥珀色，直径为99（93至105）μm。每个闭囊壳内含有一个子囊，子囊中有八个子囊孢子。根据其形态，确定病原菌为叉丝单囊壳属的一个种（1）。使用引物ITS4/ITS6扩增rDNA的ITS区域（内转录间隔区）并进行测序。对获得的531 bp序列进行BLASTn分析（1）显示，与暗叉丝单囊壳（3）的E值为0.0。该核苷酸序列已被赋予GenBank登录号EF 442023。通过将患病叶片轻轻压在健康柳叶金鸡菊植株的叶片上进行接种来确认致病性。接种了三株植株。三株未接种的植株作为对照。植株置于温度为20至28°C的温室中。接种12天后，接种的植株出现了典型的白粉病症状。未接种的植株未出现症状。致病性试验进行了两次。据我们所知，这是意大利关于柳叶金鸡菊白粉病的首次报道。此前曾报道金鸡菊属植物是菊白粉菌、黄斑球针壳、牛舌草内丝白粉菌和暗叉丝单囊壳的寄主（2,4）。凭证标本保存在都灵大学的AGROINNOVA标本馆。参考文献：（1）S. F. Altschul等人，《核酸研究》25:3389，1997。（2）U. Braun，《白粉菌科（白粉病）专论》。Cramer，柏林，民主德国，1987。（3）U. Braun和S. Takamatsu，《Schlechtendalia》4:1，2000。（4）D. F. Farr等人，《美国植物和植物产品上的真菌》。美国植物病理学会，明尼苏达州圣保罗，1989。
