A phytoplasma representative of a new subgroup, 16SrXIII-E, associated with Papaya apical curl necrosis

Papaya apical curl necrosis (PACN) has frequently been observed in several Brazilian states. Affected plants exhibit foliar chlorosis, curvature of the apex, shortening of the internodes leading to bunching of the crown leaves, necrosis of the young apical parts, leaf drop, and dieback. Naturally infected plants were sampled and subjected to PCR assays, which confirmed that a phytoplasma was associated with the disease. Sequencing of the 16S rRNA gene, conventional and computer-simulated RFLP analyses, and phylogenetic analysis allowed the determination of the PACN phytoplasma as a representative of a new subgroup, designated 16SrXIII-E. The phytoplasmas of various 16Sr groups, including 16SrI, 16SrII, 16SrX, 16SrXII, and 16SrXVII, are known to be involved in anomalies in papaya plants in several countries. However, the present study reports, for the first time, the occurrence of a 16SrXIII phytoplasma in association with a papaya disease.     

First report of a 16SrIII-B subgroup phytoplasma associated with leaf reddening, virescence and phyllody of purple coneflower

Purple coneflower plants showing leaf reddening and flower abnormalities were observed in South Bohemia (Czech Republic). Transmission electron microscopy observations showed phytoplasmas in sieve cells of symptomatic plants but not in healthy ones. Polymerase chain reactions with universal and group specific phytoplasma primers followed by restriction fragment length polymorphism analyses of 16S rDNA allowed us to classify the detected phytoplasmas into the X-disease group, ribosomal subgroup 16SrIII-B. Sequence analyses of the 16S-23S ribosomal operon (1684 bp), ribosomal protein L15, and protein translocase genes (1566 bp) confirmed the closest relationship with phytoplasmas belonging to the 16SrIII ribosomal group, specifically the 16SrIII-B subgroup. The current study reports purple coneflower as a new host for the X-disease phytoplasma group in the Czech Republic and worldwide.     

樱桃花变绿病植原体的分子鉴定

 植原体(phytoplasma)是一类没有细胞壁,不能人工培养,存在于植物筛管细胞中的类似植物病原细菌的原核生物。迄今为止,世界各地报道的1 000余种植物病害与植原体有关,引起的症状主要包括丛枝、黄化、花变绿、花变叶、花器退化等。     

Rubus stunt: a review of an important phytoplasma disease in Rubus spp.

Journal of Plant Diseases and Protection - Phytoplasmas are cell wall-less plant pathogenic bacteria that colonize the phloem of their host plants and can be transferred by plant sap-sucking...     

海南长春花黄化病植原体的16S rDNA序列分析研究

 Periwinkle(Catharanthus roseus) yellows is a common disease in Hainan. Periwinkle's leaf tissue with symptoms was assayed for phytoplasma infection by using PCR assay employing phytoplasma universal 16S rRNA gene primers (Rl6mF2/Rl6mR1). A PCR product (about 1.4 kb) was amplified from periwinkle showed yellows. Nucleotide sequencing and phylogenetic tree analysis showed that the amplified 16S rDNA contained 1 432 nucleotides, the most homology was 98.1% with the members of elm yellows group (16S r Ⅴ) and clustered in the same clade, while it was under 96.1% with other phytoplasma groups. Our results suggested that the phytoplasma sample belonged to 16S rⅤgroup and was tentatively named as Hainan periwinkle yellows phytoplasma (PY-Hn). This is the first report of existence of 16S r Ⅴ group phytoplasma in naturally infected periwinkle.     

竹小叶病植原体的分子鉴定

 2008年在杨凌采集到具有典型植原体侵染症状的菲白竹,应用植原体16S rRNA基因的通用引物对R16mF2／R16mR1和R16F2n／R16R2对其进行检测,巢式PCR得到约1.2 kb的特异性片段。对扩增片段进行测序并进行系统进化树分析,结果表明,该病原属于翠菊黄化组(Candidatus Phytoplasma asteris),与该组成员同源性均在98%以上。随后用16Sr Ⅰ组和Ⅴ组特异引物对R16（Ⅰ）F1／R16（Ⅰ）R1和R16（Ⅴ）F1／R16（Ⅴ）R1也证明其属于翠菊黄化组,RFLP 分析表明该植原体属于16SrⅠ-B亚组。植原体侵染菲白竹在中国属首次报道。     

Characterization of a phytoplasma associated with witches' broom disease of potatoes in Korea

 Symptoms of witches' broom disease caused by phytoplasma, including general stunting and yellowing, were observed in potatoes (Solanum tuberosum L.) in a storehouse on Jeju Island, Korea in 1998. Based on sequence analysis of DNA products from polymerase chain reaction (PCR)-amplified 16S ribosomal DNA and 16S–23S spacer region using universal phytoplasma primers, the phytoplasma associated with potato witches' broom disease (PWB) was identified as a member of 16S-group VIII. It was most closely related to elm AH phytoplasma (99.7% similarity, accession no. AF268895), which is in the clover proliferation (CP) subgroup. This report is the first from the East Asian continent of a plant pathogenic phytoplasma belonging to the CP subgroup and includes the nucleotide sequence of most of the potato phytoplasma 16S rDNA. Received: May 1, 2002 / Accepted: July 1, 2002     

Diverse phytoplasmas associated with maize bushy stunt disease in Peru

European Journal of Plant Pathology - Corn plants showing symptoms of midribs chlorosis, and leaf reddening, short internodes, ear proliferation, and plant growth reduction were collected in Peru...     

云南芒果变叶病植原体的分子鉴定

 植原体（phytoplasma）是一类没有细胞壁,不能离体培养的原核生物,对四环素敏感,主要存在于植物筛管细胞中。植原体主要通过叶蝉、飞虱等取食植物韧皮部的昆虫传播,也可通过菟丝子寄生和嫁接等方式传播。目前,全世界已发现1 000多种由植原体引起的植物病害,我国大陆已报道100余种与之相关的病害\[1\]。由植原体引起的病害症状主要表现为植株花器病态、小叶、丛枝、黄化等,从而导致植物产量和品质明显下降。