Lee I-M, Bottner K D, Dally E L, Davis R E
Molecular Plant Pathology Laboratory, USDA, ARS, Beltsville, MD 20705.
Plant Dis. 2008 Apr;92(4):654. doi: 10.1094/PDIS-92-4-0654B.
Purple coneflower (Echinacea purpurea (L.) Moench) is a flowering perennial plant native to North America and is widely grown as an ornamental flower. It is also grown commercially to make herbal teas and extracts purported to help strengthen the immune system. Propagation is by seed or root cuttings. Aster yellows phytoplasmas (strains belonging to group 16SrI) have been reported to be associated with purple coneflower exhibiting virescence and phyllody symptoms in the northern United States and Canada. A subgroup 16SrI-A phytoplasma was identified to be associated with symptomatic purple coneflower in Wisconsin (2). During the summers of 1994 and 2007, purple coneflower plants in Maryland sporadically exhibited symptoms resembling those caused by phytoplasma infection. Symptoms included stunting, virescence, phyllody, and abnormal flower bud proliferation from the cone. Samples from four symptomatic and two asymptomatic purple coneflower plants were collected. Total nucleic acid was extracted from leaf tissue. To assess the etiology of the disease, nested PCR with universal phytoplasma primer pair P1/P7 followed by R16F2n/R16R2 was employed for the detection of phytoplasmas (1). An amplicon of approximately 1.2 kb was amplified from all four symptomatic purple coneflower plants but not from the two asymptomatic plants. Restriction fragment length polymorphism (RFLP) patterns of 16S rDNA digested singly with restriction enzymes AluI, KpnI, HpaI, MseI, HhaI, and RsaI indicated that affected purple coneflower plants were infected by a phytoplasma belonging to aster yellows group 16SrI ('Candidatus Phytoplasma asteris'-related strains), subgroup 16SrI-B (1). Nucleotide sequence analysis of cloned 16S rDNA (GenBank Accession Nos. EU333394 and EU333395) confirmed the results from RFLP analyses. To our knowledge, this is the first report of a 16SrI-B phytoplasma infecting an Echinacea sp. in Maryland. References: (1) I.-M. Lee et al. Int. J. Syst. Bacteriol. 48:1153, 1998. (2) G. R. Stanosz et al. Plant Dis. 81:424, 1997.
紫锥花（紫松果菊，学名：Echinacea purpurea (L.) Moench）是一种多年生开花植物，原产于北美洲，作为观赏花卉被广泛种植。它也被商业化种植以制作草药茶和提取物，据称有助于增强免疫系统。繁殖方式为种子繁殖或根插繁殖。据报道，在美国北部和加拿大，紫锥花上出现的黄化和叶变症状与翠菊黄化植原体（属于16SrI组的菌株）有关。在威斯康星州，已鉴定出一种16SrI-A亚组植原体与出现症状的紫锥花有关（2）。在1994年和2007年夏季，马里兰州的紫锥花植株偶尔出现类似植原体感染引起的症状。症状包括生长迟缓、黄化、叶变以及花盘上异常的花芽增殖。采集了四株有症状和两株无症状的紫锥花植株的样本。从叶片组织中提取总核酸。为了评估该病的病因，采用通用植原体引物对P1/P7进行巢式PCR，随后用R16F2n/R16R2检测植原体（1）。从所有四株有症状的紫锥花植株中扩增出了一条约1.2 kb的扩增子，但两株无症状植株未扩增出。用限制性内切酶AluI、KpnI、HpaI、MseI、HhaI和RsaI单独消化16S rDNA后的限制性片段长度多态性（RFLP）模式表明，受影响的紫锥花植株感染了一种属于翠菊黄化组16SrI（与‘韧皮部杆菌属翠菊韧皮部杆菌’相关的菌株）的植原体，即16SrI-B亚组（1）。对克隆的16S rDNA（GenBank登录号：EU333394和EU333395）进行核苷酸序列分析，证实了RFLP分析的结果。据我们所知，这是关于16SrI-B植原体感染马里兰州紫锥花属植物的首次报道。参考文献：（1）I.-M. Lee等人，《国际系统细菌学杂志》48:1153，1998年。（2）G. R. Stanosz等人，《植物病害》81:424，1997年。
