Lee H B, Kim C J, Mun H Y
Division of Applied Bioscience and Biotechnology, College of Agriculture and Life Sciences, Chonnam National University, Gwangju 500-757, Republic of Korea. This work was supported by a grant from NIBR, and funded in part by IPET (312032-04), Republic of Korea.
Plant Dis. 2013 Oct;97(10):1385. doi: 10.1094/PDIS-10-12-0966-PDN.
Spanish needles (Bidens bipinnata L.) is an annual herb that belongs to a genus of flowering plants in family Asteraceae native to United States, and tropical regions around world. The plant produces important flavonoid compounds quercitin and hyperoside that function as anti-allergens, anti-inflammatories, anti-microbials, and anti-cancer agents. Between July and October 2011 and 2012, white superficial mycelia were observed initially on leaf and stem portions, but later progressed to the flower head. Surveys showed that the disease was widespread in Gwangju and most areas of South Korea. Abundant, necrotic, dark brown spots showing chasmothecia were frequently observed in October and were abundant on the adaxial surface of leaves. Chasmothecia were blackish brown to yellow without typical appendages. They ranged from 51.2 to 71.1 (mean 66.8) μm in diameter. Conidia were formed singly and the primary conidia were ellipsoid, rounded at the apex, truncated base, and ranged from 25.4 to 33.2 (mean 27.3) μm long × 10.2 to 12.2 (mean 11.3) μm wide. Conidiophores were erect, 60.1 to 101.3 (mean 98.3) μm long × 6.2 to 9.2 (mean 7.3) μm wide. From extracted genomic DNA, the internal transcribed spacer (ITS) region inclusive of 5.8S and 28S rDNA was amplified with ITS1F (5'-TCCGTAGGTGAACCTGCGG-3') and LR5F (5'-GCTATCCTGAGGGAAAC-3'), and LROR (5'-ACCCGCTGAACTTAAGC-3') and LR5F primer sets, respectively. rDNA ITS (GenBank Accession No. JX512555) and 28S (JX512556) homologies of the fungus (EML-BBPW1) represented 99.6% (532/534) and 100% (661/661) identity values with Podosphaera xanthii (syn. P. fusca) AB040349 and P. xanthii (syn. P. fusca) AB462798, respectively. The rDNA sequence analysis revealed that the causal fungus matched P. xanthii (syn. P. fusca), forming a xanthii/fusca group (3,4). A pathogenicity test was performed on three plants in a greenhouse. The treated leaves were sealed in vinyl pack in humid condition for 2 days. Seven days after inoculation, similar symptoms were observed on the inoculated Spanish needles plant leaves. No symptoms were observed on control plants treated with distilled water. Koch's postulates were fulfilled by re-observing the fungal pathogen on the inoculated leaves. Podosphaera (syn. Sphaerotheca) xanthii (or fusca) has been known as an ubiquitous species with a broad host range. So far, five records regarding P. xanthii (=P. fusca) have been found in plants of genus Bidens. P. xanthii has been reported to occur on B. cernua in Belarus and Switzerland. In addition, the powdery mildew species was reported to occur on B. frondosa and B. tripartita in Korea, Russia, and Switzerland (2). To our knowledge, this is the first report of powdery mildew caused by P. xanthii on Spanish needles (B. bipinnata) in Korea. References: (1) U. Braun et al. Schlechtendalia 10:91, 2003. (2) D. F. Farr and A. Y. Rossman. Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ , 2012. (3) H. B. Lee. J. Microbiol. 51:1075, 2012. (4) S. Takamatsu, et al. Persoonia 24:38, 2010.
鬼针草（Bidens bipinnata L.）是一种一年生草本植物，属于菊科开花植物属，原产于美国及世界热带地区。该植物产生重要的黄酮类化合物槲皮素和金丝桃苷，具有抗过敏、抗炎、抗菌和抗癌作用。在2011年7月至10月以及2012年期间，最初在叶片和茎部观察到白色表面菌丝体，随后发展到花头。调查显示，该病在韩国光州及大部分地区广泛传播。10月经常观察到大量带有闭囊壳的坏死深褐色斑点，且在叶片正面大量出现。闭囊壳呈黑褐色至黄色，无典型附属物。其直径范围为51.2至71.1（平均66.8）μm。分生孢子单个形成，初生分生孢子呈椭圆形，顶端圆形，基部截形，长25.4至33.2（平均27.3）μm×宽10.2至12.2（平均11.3）μm。分生孢子梗直立，长60.1至101.3（平均98.3）μm×宽6.2至9.2（平均7.3）μm。从提取的基因组DNA中，分别用ITS1F（5'-TCCGTAGGTGAACCTGCGG-3'）和LR5F（5'-GCTATCCTGAGGGAAAC-3'）以及LROR（5'-ACCCGCTGAACTTAAGC-3'）和LR5F引物对扩增包含5.8S和28S rDNA的内部转录间隔区（ITS）区域。该真菌（EML-BBPW1）的rDNA ITS（GenBank登录号JX512555）和28S（JX（此处疑有误，推测应为JX512556））与黄瓜白粉菌（Podosphaera xanthii（同义词：P. fusca））AB040349和P. xanthii（同义词：P. fusca）AB462798的同源性分别为99.6%（532/534）和100%（661/661）。rDNA序列分析表明，致病真菌与黄瓜白粉菌（Podosphaera xanthii（同义词：P. fusca））匹配，形成一个xanthii/fusca组（3,4）。在温室中对三株植物进行了致病性测试。处理后的叶片在潮湿条件下用塑料薄膜密封2天。接种7天后，在接种的鬼针草植物叶片上观察到类似症状。用蒸馏水处理的对照植物未观察到症状。通过再次观察接种叶片上的真菌病原体，科赫法则得到了验证。黄瓜白粉菌（Podosphaera（同义词：Sphaerotheca）xanthii（或fusca））是一种分布广泛、寄主范围广的物种。到目前为止，在鬼针草属植物中已发现五条关于黄瓜白粉菌（Podosphaera xanthii（=P. fusca））的记录。据报道，黄瓜白粉菌在白俄罗斯和瑞士的水鬼针草（Bidens cernua）上出现。此外，在韩国、俄罗斯和瑞士，该白粉菌物种在羽叶鬼针草（Bidens frondosa）和三叶鬼针草（Bidens tripartita）上也有报道（2）。据我们所知，这是韩国首次关于黄瓜白粉菌引起鬼针草（Bidens bipinnata）白粉病的报道。参考文献：（1）U. Braun等人，Schlechtendalia 10:91，2003。（2）D. F. Farr和A. Y. Rossman，真菌数据库，系统真菌学和微生物学实验室，美国农业部农业研究局。从http://nt.ars-grin.gov/fungaldatabases/获取，2012。（3）H. B. Lee，J. Microbiol. 51:1075，2012。（4）S. Takamatsu等人，Persoonia 24:38，2010。
