Natural occurrence, identification and transmission of the phytoplasma associated with flax phyllody and stem fasciation in Pakistan

Flax plants (Linum usitatissimum) of the white (album) flower variety exhibiting typical phytoplasma-like symptoms were found for the first time in Pakistan during 2011. The symptoms included floral virescence, phyllody, little leaf, stunting and stem fasciation. Light microscopy of hand-cut stem sections treated with Dienes’ stain showed blue areas in the phloem region of symptomatic plants. To confirm phytoplasma infection, total DNA was extracted separately from five plants showing virescence/phyllody and from five others showing fasciation, and was amplified by nested PCR using universal 16S rDNA phytoplasma primers P1/P7 followed by R16F2n/R16R2. All samples from plants with virescence/phyllody and fasciation yielded a 1,250 bp PCR product, and identical RFLP profiles using the enzymes AluI and HpaII. Direct sequencing of the 16S rDNA of one representative PCR amplicon (GenBank Accession No. JX567504 for phyllody and Accession No. JX567505 for fasciation) showed highest sequence identity (99%) with 16SrII ‘Candidatus Phytoplasma aurantifolia’ phytoplasmas, and phylogenetic analysis placed the phytoplasma in subgroup 16SrII-D. Disease was successfully transmitted by grafting and by the leafhopper Orosius albicinctus. To our knowledge, flax is a new natural host for 16SrII-D phytoplasmas in Pakistan.     

Detection and molecular characterization of phytoplasma associated with chickpea phyllody disease in south India

Chickpea (Cicer arietinum L.) plants showing typical symptoms of infection by a phytoplasma that causes phyllody disease have been commonly observed in recent years in parts of south India. The symptoms included pale green leaves, bushy appearance due to excessive stunting of shoots, reduced internodal length and excessive axillary proliferation. The causal agent of the phyllody disease was identified based on symptoms, amplification of 16S rDNA of the phytoplasma by polymerase chain reaction (PCR) from infected samples, as well as by sequencing and phylogenetic analysis. First round PCR and nested-PCR protocols were standardized for improved efficiency and reliability of the diagnostic protocols. Using the primers P1/P7 and R16F2n/R16R2, 1,800?bp and 1,200?bp size products were amplified in first round PCR and nested-PCR protocols, respectively. The PCR product was cloned and sequenced and compared with the reference phytoplasma sequences from the database (NCBI). The Indian chickpea phyllody phytoplasma 16S rDNA sequences shared the highest nucleotide identity (>98%) with the 16S rII group phytoplasma candidates, also infecting chickpea from Australia and Pakistan. This is the first report of a phytoplasma of the 16SrII-group infecting chickpea from India. The genetic similarities and the potential threat of this new disease to chickpea cultivation in India are discussed.     

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。     

三叶草绿变病植原体的分子鉴定

三叶草(Trifolium pratense Linn.)为车轴草属,蝶形花科多年生草本植物,原产亚洲南部和欧洲东南部,是一种世界性分布与栽培的优良牧草.因其花叶兼优、草姿美、绿期长而具有较高的观赏价值,近几年作为草坪用草被广泛种植.在自然条件下,三叶草很容易受到不同种植原体的侵染,国外已报道的侵染三叶草的植原体有:三叶草绿变植原体( Clover phyllody phytoplasma,CPh)和三叶草增殖植原体(Clover proliferation phytoplasma,CP)等,这些植原体分别属于16SrI组和16SrⅥ组[1,2].     

Molecular and biologic characterization of a phytoplasma associated with <Emphasis Type="Italic">Brassica campestris</Emphasis> phyllody disease in Punjab province,Pakistan

A phytoplasma-associated disease was identified in Brassica campestris (sarson) plants during a survey conducted in Punjab province of Pakistan in 2014–2016. The symptomatic plants showed characteristic symptoms of phyllody and witches’ broom. Phytoplasma presence was detected by polymerase chain reaction on 16S ribosomal and tuf DNAs, followed by RFLP analysis and sequence comparison of the 16S rRNA and tuf genes. The phytoplasma detected was classified in a new ribosomal subgroup designed 16SrIX-H. The phytoplasma presence in phloem tissues of symptomatic sarson samples was also confirmed through light microscopy and transmission studies to healthy plants through dodder and the leafhopper Orosius albicinctus. This is the first report of identification of 16SrIX-H subgroup phytoplasma associated with sarson and its natural vector in Pakistan.     

First report of Crepis phyllody disease associated with phytoplasma in Crepis foetida in walnut orchard in Turkey

Journal of Plant Diseases and Protection - In a walnut orchard in Turkey’s Mersin province in the summer of 2021, phytoplasma related symptoms such as abnormal formations in flowers...     

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。     

Molecular identification of a new phytoplasma associated with alfalfa witches'-broom in oman

ABSTRACT Alfalfa (Medicago sativa) plants showing witches'-broom symptoms typical of phytoplasmas were observed from Al-Batinah, Al-Sharqiya, Al-Bureimi, and interior regions of the Sultanate of Oman. Phytoplasmas were detected from all symptomatic samples by the specific amplification of their 16S-23S rRNA gene. Polymerase chain reaction (PCR), utilizing phytoplasma-specific universal primer pairs, consistently amplified a product of expected lengths when DNA extract from symptomatic samples was used as template. Asymptomatic plant samples and the negative control yielded no amplification. Restriction fragment length polymorphism profiles of PCR-amplified 16S-23S rDNA of alfalfa using the P1/P7 primer pair identified phytoplasmas belonging to peanut witches'-broom group (16SrII or faba bean phyllody). Restriction enzyme profiles showed that the phytoplasmas detected in all 300 samples belonged to the same ribosomal group. Extensive comparative analyses on P1/P7 amplimers of 20 phytoplasmas with Tru9I, Tsp509I, HpaII, TaqI, and RsaI clearly indicated that this phytoplasma is different from all the other phytoplasmas employed belonging to subgroup 16SrII, except tomato big bud phytoplasma from Australia, and could be therefore classified in subgroup 16SrII-D. The alfalfa witches'-broom (AlfWB) phytoplasma P1/P7 PCR product was sequenced directly after cloning and yielded a 1,690-bp product. The homology search showed 99% similarity (1,667 of 1,690 base identity) with papaya yellow crinkle (PapayaYC) phytoplasma from New Zealand. A phylogenetic tree based on 16S plus spacer regions sequences of 35 phytoplasmas, mainly from the Southern Hemisphere, showed that AlfWB is a new phytoplasma species, with closest relationships to PapayaYC phytoplasmas from New Zealand and Chinese pigeon pea witches'-broom phytoplasmas from Taiwan but distinguishable from them considering the different associated plant hosts and the extreme geographical isolation.     

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