Gao R, Wang J, Li X D, Zhu X P, Tian G Z
Department of Plant Pathology, College of Plant Protection, Shandong Agricultural University, Tai'an 271018, China.
Research Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry, Beijing 100091, China.
Plant Dis. 2007 May;91(5):635. doi: 10.1094/PDIS-91-5-0635C.
Bumald spirea (Spiarea bumalda Burv.) is an important ornamental tree widely grown in northern China. In August of 2006, spirea plants exhibiting symptoms of witches'-broom, stunting, yellowing, and shoot dieback were found at an incidence of 5 to 15% in Qingzhou City, Shandong Province, China. Total DNA was extracted separately from 0.1 g of phloem tissue from leaf midribs and stems of six symptomatic and six asymptomatic plants with a modified cetyltriethylammonium bromide (CTAB) method (3). Resulting DNA samples were analyzed for phytoplasma DNA by a nested PCR assay using phytoplasma universal 16S rDNA gene primer pairs R16mF2/R16mR1 and R16F2n/R16R2 (2). These primers amplified 1.5- and 1.2-kb products, respectively, from DNA of all symptomatic plants only. Restriction fragment length polymorphism (RFLP) analysis of the 1.2-kb 16S rDNA product using enzymes AluI, MseI, and HhaI indicated that all symptomatic plants contained a group 16SrI (aster yellows group) subgroup B (16SrI-B) phytoplasma strain (4). A 16S rDNA sequence derived from this strain (GenBank Accession No. EF176608) was most similar (99.8 and 99.6%) to those of severe aster yellows (GenBank Accession No. M86340) and Maryland aster yellows (GenBank Accession No. AF322644) phytoplasmas, respectively, thereby confirming strain identity based on RFLP analysis. A phytoplasma (Spiarea stunt phytoplasma, GenBank Accession No. AF190228), which belongs to X-disease group (16SrIII), was reported to infect spirea and probably be lethal to S. tomentosa in New York (1,4). The phytoplasma reported here shared low identity (90.8%) with Spiarea stunt phytoplasma, but also caused dieback of spirea shoots. The epidemiology and economic impact of this disease need further intensive investigation. To our knowledge, this is the first report of spirea witches'-broom disease and of its association with a subgroup 16SrI-B phytoplasma in China. References: (1) H. M. Griffiths et al. Can. J. Plant Pathol. 16:255, 1994. (2) D. E. Gundersen and I.-M. Lee. Phytopathol. Mediterr. 35:144, 1996. (3) Y. Qi et al. Biotechnol. Bull. 4:44, 2004. (4) The IRPCM Phytoplasma/Spiroplasma Working Team-Phytoplasma Taxonomy Group. Int. J. Syst. Bacteriol. 54:1243, 2004.
珍珠绣线菊（Spiarea bumalda Burv.）是中国北方广泛种植的一种重要观赏树木。2006年8月，在中国山东省青州市发现了表现出丛枝、矮化、黄化和嫩梢枯死症状的绣线菊植株，发病率为5%至15%。采用改良的十六烷基三乙基溴化铵（CTAB）法（3），分别从6株有症状和6株无症状植株的叶中脉和茎的0.1 g韧皮部组织中提取总DNA。使用植原体通用16S rDNA基因引物对R16mF2/R16mR1和R16F2n/R16R2（2），通过巢式PCR分析对所得DNA样本进行植原体DNA检测。这些引物分别仅从所有有症状植株的DNA中扩增出1.5 kb和1.2 kb的产物。使用AluI、MseI和HhaI酶对1.2 kb的16S rDNA产物进行限制性片段长度多态性（RFLP）分析表明，所有有症状植株均含有16SrI组（紫菀黄化组）亚组B（16SrI-B）植原体菌株（4）。源自该菌株的16S rDNA序列（GenBank登录号EF176608）分别与严重紫菀黄化植原体（GenBank登录号M86340）和马里兰紫菀黄化植原体（GenBank登录号AF322644）的序列最为相似（99.8%和99.6%），从而基于RFLP分析确认了菌株身份。据报道，一种属于X病组（16SrIII）的植原体（绣线菊矮化植原体，GenBank登录号AF190228）感染绣线菊，可能对纽约的绒毛绣线菊具有致死性（（1,4））。此处报道的植原体与绣线菊矮化植原体的同源性较低（90.8%），但也导致了绣线菊嫩梢枯死。这种病害的流行病学和经济影响需要进一步深入研究。据我们所知，这是中国关于绣线菊丛枝病及其与16SrI-B亚组植原体关联的首次报道。参考文献：（1）H. M. Griffiths等人，《加拿大植物病理学杂志》16:255，1994年。（2）D. E. Gundersen和I.-M. Lee，《地中海植物病理学》35:144，1996年。（3）Y. Qi等人，《生物技术通报》4:44，2004年。（4）国际植物原体/螺旋原体研究小组 - 植物原体分类学组，《国际系统与细菌学杂志》54:1243，2004年。
