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Assunta Bertaccini - One of the best experts on this subject based on the ideXlab platform.
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Occurrence of two 'Candidatus Phytoplasma asteris' - related Phytoplasmas in poplar trees in Serbia.
Bulletin of Insectology, 2020Co-Authors: J. Mitrovic, Nicoletta Contaldo, Samanta Paltrinieri, Assunta Bertaccini, Bojan Duduk, S MainiAbstract:During a survey carried out in Serbia in black poplar trees, typical symptoms of Phytoplasma presence were observed such as yellowing and undersize of the leaves, witches’ broom and decline. Survey for Phytoplasma presence in Belgrade and in its surrounding allow to identify Phytoplasmas belonging to ‘Candidatus Phytoplasma asteris’ group, in particular to two 16SrI subgroups 16SrI-P and 16SrI-A. Blast search of obtained strain in subgroup 16SrI-P of the 16SrDNA sequence showed 100% homology with aster yellows Phytoplasma strain from poplar from Croatia.
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Epidemiological aspects of Phytoplasmas in Chilean grapevines
Bulletin of Insectology, 2020Co-Authors: V. Longone, Samanta Paltrinieri, Assunta Bertaccini, F. González, Alan Zamorano, Ana María Pino, J. Araya, V. Díaz, Alberto Calari, L. PicciauAbstract:Some Auchenorrhyncha specimens were captured, identified and tested to verify Phytoplasma presence in Chilean vineyards; many of them belong to the subfamily Delthocephalinae and Agalliinae (family Cicadellidae) and to the families Cixiidae and Delphacidae, all known as potential Phytoplasma vectors. Several individuals were positives to Phytoplasma presence, in particu- lar Amplicephalus curtulus Linnavuori & De Long, in which were detected Phytoplasmas belonging to subgroup16SrI-B and 16SrXII-A, and Paratanus exitiosus (Beamer) positive to Phytoplasmas of the subgroups 16SrI-B, 16SrVII-A and 16SrXII-A. Phytoplasmas belonging to subgroup 16SrI-B and 16SrVII-A were identified in Convolvulus arvensis L. and Polygonum avicu- lare L.; to subgroup 16SrXII-A in C. arvensis; and to subgroup16SrVII-A in Galega officinalis L. In three cases grapevine sam- ples, weeds and insects collected in the same vineyard were positives to Phytoplasmas of the same subgroup.
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Phytoplasmas in Brazil: an update
Bulletin of Insectology, 2020Co-Authors: H G Montano, Assunta Bertaccini, J P Pimentel, J. O. Cunha Junior, S MainiAbstract:In Brazil a number of plant species are affected by Phytoplasma diseases, comprising wild and cultivated crops. Amongst the recently botanical species reported as natural Phytoplasma host is sweet orange (Citrus sinensis) with huanglongbing symptoms. The majority of Phytoplasmas identified in Brazil belongs to groups 16SrI and 16SrIII.
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Phytoplasma presence in carrot seedlings
Australasian Plant Disease Notes, 2020Co-Authors: Eleonora Satta, Gaia Carminati, Assunta BertacciniAbstract:Phytoplasmas are cell wall lacking bacteria, insect transmitted, and worldwide infecting carrots with severe epidemics. Molecular tests on up to 4-month-old carrot seedlings from Phytoplasma-positive seed batches, carried out under insect proof conditions, indicated that in the early stages of the plant development, the Phytoplasma-infected and not water-stressed plants are asymptomatic. The Phytoplasma seed transmission could represent a dangerous source of infection.
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Multilocus Genetic Characterization of Phytoplasmas
Phytoplasmas: Plant Pathogenic Bacteria - III, 2019Co-Authors: Marta Martini, Fabio Quaglino, Assunta BertacciniAbstract:Classification of Phytoplasmas into 16S ribosomal groups and subgroups and ‘Candidatus Phytoplasma’ species designation have been primarily based on the conserved 16S rRNA gene. However, distinctions among closely related ‘Ca. Phytoplasma’ species and strains based on 16S rRNA gene alone have limitations imposed by the high degree of rRNA nucleotide sequence conservation across diverse Phytoplasma lineages and by the presence in a Phytoplasma genome of two, sometimes sequence heterogeneous, copies of this gene. Thus, in recent years, moderately conserved genes have been used as additional genetic markers with the aim to enhance the resolving power in delineating distinct Phytoplasma strains among members of some 16S ribosomal subgroups. The present chapter is divided in two parts: the first part describes the non-ribosomal single-copy genes less conserved (housekeeping genes) such as ribosomal protein (rp), secY, secA, rpoB, tuf, and groEL genes, which have been extensively used for differentiation across the majority of Phytoplasmas; the second part describes the differentiation of Phytoplasmas in the diverse ribosomal groups using multiple genes including housekeeping genes and variable genes encoding surface proteins.
R E Davis - One of the best experts on this subject based on the ideXlab platform.
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should candidatus Phytoplasma be retained within the order acholeplasmatales
International Journal of Systematic and Evolutionary Microbiology, 2015Co-Authors: Y Zhao, R E DavisAbstract:Phytoplasmas are a diverse but phylogenetically coherent group of cell-wall-less bacteria affiliated with the class Mollicutes . Due to difficulties in establishing axenic culture, Phytoplasmas were assigned to a provisional genus, ‘Candidatus Phytoplasma’, and the genus was embraced within the order Acholeplasmatales . However, Phytoplasmas differ significantly from species of the genus Acholeplasma in their habitat specificities, modes of life, metabolic capabilities, genomic architectures, and phylogenetic positions. This communication describes the unique ecological, nutritional, biochemical, genomic and phylogenetic properties that distinguish Phytoplasmas from species of the genus Acholeplasma and all other taxa in the class Mollicutes . Since such distinguishing properties of the Phytoplasmas are not referable to the descriptions of the order Acholeplasmatales and of all other existing orders, namely Mycoplasmatales , Entomoplasmatales and Anaeroplasmatales , this communication raises the question of whether ‘ Candidatus Phytoplasma ’ should be retained in the order Acholeplasmatales or whether a novel provisional order and family should be created to accommodate the genus ‘ Ca. Phytoplasma ’.
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new subgroup 16sriii y Phytoplasmas associated with false blossom diseased cranberry vaccinium macrocarpon plants and with known and potential insect vectors in new jersey
European Journal of Plant Pathology, 2014Co-Authors: J Polashock, K D Bottnerparker, P G Bagadia, C Rodriguezsaona, Y Zhao, R E DavisAbstract:The identity of the presumed Phytoplasmal pathogen associated with cranberry false-blossom disease has never been fully clarified. In the present study a molecular-based procedure was employed to determine the identity of the Phytoplasma. Tissues of cranberry plants exhibiting cranberry false-blossom symptoms were collected from multiple bogs on each of three randomly selected commercial cranberry farms in New Jersey. Leafhoppers, including the known vector Limotettix vaccinii (Van Duzee) (=Scleroracus vaccinii, Euscellis striatulus) and the sharp-nosed leafhopper Scaphytopius magdalensis (Provancher), a known vector of blueberry stunt disease, were collected from two different farms in New Jersey. Nested PCR assays and RFLP analysis of 16S rRNA gene sequences were employed for the detection and identification of the associated Phytoplasmas. All of 20 cranberry plants sampled and five out of 14 batches of leafhoppers tested positive for Phytoplasma. Virtual RFLP and sequence analyses revealed that all the associated Phytoplasmas were members or variants of a new subgroup, 16SrIII-Y. Phylogenetic analysis of 16S rRNA sequences indicated that cranberry false-blossom Phytoplasma strains represented a lineage distinct from other 16SrIII subgroups. This is the first report confirming that a new Phytoplasma (designated as a new subgroup 16SrIII-Y) is associated with cranberry false-blossom disease and associated with both leafhopper species in New Jersey.
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candidatus Phytoplasma malaysianum a novel taxon associated with virescence and phyllody of madagascar periwinkle catharanthus roseus
International Journal of Systematic and Evolutionary Microbiology, 2013Co-Authors: Naghmeh Nejat, R E Davis, Ganesan Vadamalai, N A Harrison, Kamaruzaman Sijam, Matthew Dickinson, Siti Nor Akmar Abdullah, Y ZhaoAbstract:This study addressed the taxonomic position and group classification of a Phytoplasma responsible for virescence and phyllody symptoms in naturally diseased Madagascar periwinkle plants in western Malaysia. Unique regions in the 16S rRNA gene from the Malaysian periwinkle virescence (MaPV) Phytoplasma distinguished the Phytoplasma from all previously described ‘ Candidatus Phytoplasma ’ species. Pairwise sequence similarity scores, calculated through alignment of full-length 16S rRNA gene sequences, revealed that the MaPV Phytoplasma 16S rRNA gene shared 96.5 % or less sequence similarity with that of previously described ‘ Ca. Phytoplasma ’ species, justifying the recognition of the MaPV Phytoplasma as a reference strain of a novel taxon, ‘Candidatus Phytoplasma malaysianum’. The 16S rRNA gene F2nR2 fragment from the MaPV Phytoplasma exhibited a distinct restriction fragment length polymorphism (RFLP) profile and the pattern similarity coefficient values were lower than 0.85 with representative Phytoplasmas classified in any of the 31 previously delineated 16Sr groups; therefore, the MaPV Phytoplasma was designated a member of a new 16Sr group, 16SrXXXII. Phytoplasmas affiliated with this novel taxon and the new group included diverse strains infecting periwinkle, coconut palm and oil palm in Malaysia. Three Phytoplasmas were characterized as representatives of three distinct subgroups, 16SrXXXII-A, 16SrXXXII-B and 16SrXXXII-C, respectively.
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ancient recurrent phage attacks and recombination shaped dynamic sequence variable mosaics at the root of Phytoplasma genome evolution
Proceedings of the National Academy of Sciences of the United States of America, 2008Co-Authors: R E Davis, R Jomantiene, Yan ZhaoAbstract:Mobile genetic elements have impacted biological evolution across all studied organisms, but evidence for a role in evolutionary emergence of an entire phylogenetic clade has not been forthcoming. We suggest that mobile element predation played a formative role in emergence of the Phytoplasma clade. Phytoplasmas are cell wall-less bacteria that cause numerous diseases in plants. Phylogenetic analyses indicate that these transkingdom parasites descended from Gram-positive walled bacteria, but events giving rise to the first Phytoplasma have remained unknown. Previously we discovered a unique feature of Phytoplasmal genome architecture, genes clustered in sequence-variable mosaics (SVMs), and suggested that such structures formed through recurrent, targeted attacks by mobile elements. In the present study, we discovered that cryptic prophage remnants, originating from phages in the order Caudovirales, formed SVMs and comprised exceptionally large percentages of the chromosomes of ‘Candidatus Phytoplasma asteris’-related strains OYM and AYWB, occupying nearly all major nonsyntenic sections, and accounting for most of the size difference between the two genomes. The clustered phage remnants formed genomic islands exhibiting distinct DNA physical signatures, such as dinucleotide relative abundance and codon position GC values. Phytoplasma strain-specific genes identified as phage morons were located in hypervariable regions within individual SVMs, indicating that prophage remnants played important roles in generating Phytoplasma genetic diversity. Because no SVM-like structures could be identified in genomes of ancestral relatives including Acholeplasma spp., we hypothesize that ancient phage attacks leading to SVM formation occurred after divergence of Phytoplasmas from acholeplasmas, triggering evolution of the Phytoplasma clade.
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genetic diversity among Phytoplasmas infecting opuntia species virtual rflp analysis identifies new subgroups in the peanut witches broom Phytoplasma group
International Journal of Systematic and Evolutionary Microbiology, 2008Co-Authors: R E Davis, Hairu Chen, Y ZhaoAbstract:Phytoplasmas were detected in cactus (Opuntia species) plants exhibiting witches'-broom disease symptoms in Yunnan Province, south-western China. Comparative and phylogenetic analyses of 16S rRNA gene sequences indicated that an overwhelming majority of the cactus-infecting Phytoplasmas under study belonged to the peanut witches'-broom Phytoplasma group (16SrII). Genotyping through use of computer-simulated restriction fragment length polymorphism (RFLP) analysis of 16S rRNA genes revealed a remarkable genetic diversity among these cactus-infecting Phytoplasma strains. Based on calculated coefficients of RFLP pattern similarities, seven new 16SrII subgroups were recognized, bringing the total of described group 16SrII subgroups to 12 worldwide. Geographical areas differed from one another in the extent of genetic diversity among cactus-infecting Phytoplasma strains. The findings have implications for relationships between ecosystem distribution and the emergence of group 16SrII subgroup diversity.
Y Zhao - One of the best experts on this subject based on the ideXlab platform.
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should candidatus Phytoplasma be retained within the order acholeplasmatales
International Journal of Systematic and Evolutionary Microbiology, 2015Co-Authors: Y Zhao, R E DavisAbstract:Phytoplasmas are a diverse but phylogenetically coherent group of cell-wall-less bacteria affiliated with the class Mollicutes . Due to difficulties in establishing axenic culture, Phytoplasmas were assigned to a provisional genus, ‘Candidatus Phytoplasma’, and the genus was embraced within the order Acholeplasmatales . However, Phytoplasmas differ significantly from species of the genus Acholeplasma in their habitat specificities, modes of life, metabolic capabilities, genomic architectures, and phylogenetic positions. This communication describes the unique ecological, nutritional, biochemical, genomic and phylogenetic properties that distinguish Phytoplasmas from species of the genus Acholeplasma and all other taxa in the class Mollicutes . Since such distinguishing properties of the Phytoplasmas are not referable to the descriptions of the order Acholeplasmatales and of all other existing orders, namely Mycoplasmatales , Entomoplasmatales and Anaeroplasmatales , this communication raises the question of whether ‘ Candidatus Phytoplasma ’ should be retained in the order Acholeplasmatales or whether a novel provisional order and family should be created to accommodate the genus ‘ Ca. Phytoplasma ’.
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new subgroup 16sriii y Phytoplasmas associated with false blossom diseased cranberry vaccinium macrocarpon plants and with known and potential insect vectors in new jersey
European Journal of Plant Pathology, 2014Co-Authors: J Polashock, K D Bottnerparker, P G Bagadia, C Rodriguezsaona, Y Zhao, R E DavisAbstract:The identity of the presumed Phytoplasmal pathogen associated with cranberry false-blossom disease has never been fully clarified. In the present study a molecular-based procedure was employed to determine the identity of the Phytoplasma. Tissues of cranberry plants exhibiting cranberry false-blossom symptoms were collected from multiple bogs on each of three randomly selected commercial cranberry farms in New Jersey. Leafhoppers, including the known vector Limotettix vaccinii (Van Duzee) (=Scleroracus vaccinii, Euscellis striatulus) and the sharp-nosed leafhopper Scaphytopius magdalensis (Provancher), a known vector of blueberry stunt disease, were collected from two different farms in New Jersey. Nested PCR assays and RFLP analysis of 16S rRNA gene sequences were employed for the detection and identification of the associated Phytoplasmas. All of 20 cranberry plants sampled and five out of 14 batches of leafhoppers tested positive for Phytoplasma. Virtual RFLP and sequence analyses revealed that all the associated Phytoplasmas were members or variants of a new subgroup, 16SrIII-Y. Phylogenetic analysis of 16S rRNA sequences indicated that cranberry false-blossom Phytoplasma strains represented a lineage distinct from other 16SrIII subgroups. This is the first report confirming that a new Phytoplasma (designated as a new subgroup 16SrIII-Y) is associated with cranberry false-blossom disease and associated with both leafhopper species in New Jersey.
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candidatus Phytoplasma malaysianum a novel taxon associated with virescence and phyllody of madagascar periwinkle catharanthus roseus
International Journal of Systematic and Evolutionary Microbiology, 2013Co-Authors: Naghmeh Nejat, R E Davis, Ganesan Vadamalai, N A Harrison, Kamaruzaman Sijam, Matthew Dickinson, Siti Nor Akmar Abdullah, Y ZhaoAbstract:This study addressed the taxonomic position and group classification of a Phytoplasma responsible for virescence and phyllody symptoms in naturally diseased Madagascar periwinkle plants in western Malaysia. Unique regions in the 16S rRNA gene from the Malaysian periwinkle virescence (MaPV) Phytoplasma distinguished the Phytoplasma from all previously described ‘ Candidatus Phytoplasma ’ species. Pairwise sequence similarity scores, calculated through alignment of full-length 16S rRNA gene sequences, revealed that the MaPV Phytoplasma 16S rRNA gene shared 96.5 % or less sequence similarity with that of previously described ‘ Ca. Phytoplasma ’ species, justifying the recognition of the MaPV Phytoplasma as a reference strain of a novel taxon, ‘Candidatus Phytoplasma malaysianum’. The 16S rRNA gene F2nR2 fragment from the MaPV Phytoplasma exhibited a distinct restriction fragment length polymorphism (RFLP) profile and the pattern similarity coefficient values were lower than 0.85 with representative Phytoplasmas classified in any of the 31 previously delineated 16Sr groups; therefore, the MaPV Phytoplasma was designated a member of a new 16Sr group, 16SrXXXII. Phytoplasmas affiliated with this novel taxon and the new group included diverse strains infecting periwinkle, coconut palm and oil palm in Malaysia. Three Phytoplasmas were characterized as representatives of three distinct subgroups, 16SrXXXII-A, 16SrXXXII-B and 16SrXXXII-C, respectively.
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the i phyclassifier an interactive online tool for Phytoplasma classification and taxonomic assignment
Methods of Molecular Biology, 2013Co-Authors: Y Zhao, Jonathan Shao, Robert E. DavisAbstract:: The iPhyClassifier is an internet-based research tool for quick identification and classification of diverse Phytoplasmas. The iPhyClassifier simulates laboratory restriction enzyme digestions and subsequent gel electrophoresis and generates virtual restriction fragment length polymorphism (RFLP) patterns. Based on RFLP pattern similarity coefficient scores, the iPhyClassifier gives instant suggestions on group and subgroup classification status of the Phytoplasma strains under study. The iPhyClassifier also aligns the query sequences with that of reference strains of all previously described 'Candidatus Phytoplasma' species, -calculates sequence similarity scores, and assigns the Phytoplasmas under study into respective 'Ca. Phytoplasma' species as related strains according to the guidelines set forth by the Phytoplasma Taxonomy Group of the International Research Program on Comparative Mycoplasmology. Additional functions of the iPhyClassifier include delineation of potentially new Phytoplasma groups and subgroups as well as new 'Ca. Phytoplasma' species. This chapter describes the program components, the operational procedure, and the underlying principles of the iPhyClassifier operation. The chapter also provides hints on how to interpret the results.
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candidatus Phytoplasma costaricanum a novel Phytoplasma associated with an emerging disease in soybean glycine max
International Journal of Systematic and Evolutionary Microbiology, 2011Co-Authors: K D Bottnerparker, Y Zhao, W Villalobos, Lisela MoreiraAbstract:A novel Phytoplasma, designated strain SoyST1c1, associated with a newly emerging disease in soybean (Glycine max), known as soybean stunt (SoyST), was found in 2002 in a soybean plantation in Alajuela Province, Costa Rica. The same Phytoplasma, or a very closely related strain, also infected sweet pepper (Capsicum annuum) with purple vein syndrome (SwPPV) and passion fruit vine (Passiflora edulis) with bud proliferation disease (PasFBP) in the same region. Sequence analysis of cloned 16S rRNA gene sequences (GenBank accession nos FJ226068–FJ226073 and HQ225624–HQ225635) indicated that all three affected plants were infected by Phytoplasmas that shared <97.5 % sequence similarity with previously described Phytoplasmas. The SoyST-causing Phytoplasma represents a new taxon, most closely related to Phytoplasma group 16SrI and 16SrXII strains. Virtual RFLP analysis indicated that the SoyST-causing Phytoplasma and its closely related strains represent a novel 16Sr group, designated 16SrXXXI. Phylogenetic analysis of 16S rRNA gene sequences from the new Phytoplasma strains, those previously described as ‘Candidatus Phytoplasma spp.’ and other distinct, as yet unnamed, Phytoplasmas indicated that the SoyST-causing Phytoplasma represents a distinct lineage within the aster yellows/stolbur branch on the phylogenetic tree. On the basis of its unique 16S rRNA gene sequence and biological properties, strain SoyST1c1 represents a novel taxon, for which the name ‘Candidatus Phytoplasma costaricanum’ is proposed with SoyST1c1 as the reference strain.
Shigetou Namba - One of the best experts on this subject based on the ideXlab platform.
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spatiotemporal dynamics and quantitative analysis of Phytoplasmas in insect vectors
Scientific Reports, 2020Co-Authors: Hiroaki Koinuma, Kensaku Maejima, Ryosuke Tokuda, Yugo Kitazawa, Takamichi Nijo, Kohei Kumita, Akio Miyazaki, Shigetou Namba, Yasuyuki YamajiAbstract:Phytoplasmas are transmitted by insect vectors in a persistent propagative manner; however, detailed movements and multiplication patterns of Phytoplasmas within vectors remain elusive. In this study, spatiotemporal dynamics of onion yellows (OY) Phytoplasma in its vector Macrosteles striifrons were investigated by immunohistochemistry-based 3D imaging, whole-mount fluorescence staining, and real-time quantitative PCR. The results indicated that OY Phytoplasmas entered the anterior midgut epithelium by seven days after acquisition start (daas), then moved to visceral muscles surrounding the midgut and to the hemocoel at 14–21 daas; finally, OY Phytoplasmas entered into type III cells of salivary glands at 21–28 daas. The anterior midgut of the alimentary canal and type III cells of salivary glands were identified as the major sites of OY Phytoplasma infection. Fluorescence staining further revealed that OY Phytoplasmas spread along the actin-based muscle fibers of visceral muscles and accumulated on the surfaces of salivary gland cells. This accumulation would be important for Phytoplasma invasion into salivary glands, and thus for successful insect transmission. This study demonstrates the spatiotemporal dynamics of Phytoplasmas in insect vectors. The findings from this study will aid in understanding of the underlying mechanism of insect-borne plant pathogen transmission.
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Comprehensive screening of antimicrobials to control Phytoplasma diseases using an in vitro plant-Phytoplasma co-culture system.
Microbiology, 2018Co-Authors: Kazuyuki Tanno, Hiroaki Koinuma, Kensaku Maejima, Yugo Kitazawa, Takamichi Nijo, Akio Miyazaki, Yasuyuki Yamaji, Nozomu Iwabuchi, Masayoshi Hashimoto, Shigetou NambaAbstract:Phytoplasmas are plant-pathogenic bacteria that infect many important crops and cause serious economic losses worldwide. However, owing to an inability to culture Phytoplasmas, screening of antimicrobials on media is difficult. The only antimicrobials being used to control Phytoplasmas are tetracycline-class antibiotics. In this study, we developed an accurate and efficient screening method to evaluate the effects of antimicrobials using an in vitro plant–Phytoplasma co-culture system. We tested 40 antimicrobials, in addition to tetracycline, and four of these (doxycycline, chloramphenicol, thiamphenicol and rifampicin) decreased the accumulation of ‘Candidatus (Ca.) Phytoplasma asteris'. The Phytoplasma was eliminated from infected plants by the application of both tetracycline and rifampicin. We also compared nucleotide sequences of rRNAs and amino acid sequences of proteins targeted by antimicrobials between Phytoplasmas and other bacteria. Since antimicrobial target sequences were conserved among various Phytoplasma species, the antimicrobials that decreased accumulation of ‘Ca. P. asteris' may also have been effective against other Phytoplasma species. These approaches will provide new strategies for Phytoplasma disease management.
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Exploring the Phytoplasmas, plant pathogenic bacteria
Journal of General Plant Pathology, 2014Co-Authors: Kensaku Maejima, Kenro Oshima, Shigetou NambaAbstract:Phytoplasmas are plant pathogenic bacteria associated with devastating damage to over 700 plant species worldwide. It is agriculturally important to identify factors involved in their pathogenicity and to discover effective measures to control Phytoplasma diseases. Despite their economic importance, Phytoplasmas remain the most poorly characterized plant pathogens, primarily because efforts at in vitro culture, gene delivery, and mutagenesis have been unsuccessful. However, recent molecular studies have revealed unique biological features of Phytoplasmas. This review summarizes the history and recent progress in Phytoplasma research, focusing on (1) the discovery of Phytoplasmas, (2) molecular classification of Phytoplasmas, (3) diagnosis of Phytoplasma diseases, (4) reductive evolution of the genomes, (5) characteristic features of the plasmids, (6) molecular mechanisms of insect transmissibility, and (7) virulence factors involved in their unique symptoms.
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candidatus Phytoplasma oryzae a novel Phytoplasma taxon associated with rice yellow dwarf disease
International Journal of Systematic and Evolutionary Microbiology, 2003Co-Authors: Heeyoung Jung, T Sawayanagi, Shigeyuki Kakizawa, Hisashi Nishigawa, Shinichi Miyata, Kenro Oshima, Masashi Ugaki, Tadaaki Hibi, Porntip Wongkaew, Shigetou NambaAbstract:In addition to rice yellow dwarf (RYD) Phytoplasma, several Phytoplasmas infect gramineous plants, including rice orange leaf, bermuda grass white leaf, brachiaria grass white leaf and sugarcane white leaf Phytoplasmas. To investigate whether the RYD Phytoplasma is a discrete, species-level taxon, several isolates of the aforementioned Phytoplasmas were analysed using PCR-amplified 16S rDNA sequences. Two RYD isolates, RYD-JT and RYD-Th, were almost identical (99·2 %), but were distinct (similarities of 96·3–97·9 %) from other Phytoplasma isolates of the RYD 16S-group. The notion that the RYD Phytoplasma constitutes a unique taxon is also supported by its unique insect vector (Nephotettix sp.), its unique host plant in nature (rice) and its limited geographical distribution (Asia). In Southern blot analysis, chromosomal and extrachromosomal DNA probes of the RYD Phytoplasma reportedly did not hybridize with those of closely related Phytoplasmas. These properties of the RYD Phytoplasma clearly indicate that it represents a novel taxon, ‘Candidatus Phytoplasma oryzae’.
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candidatus Phytoplasma ziziphi a novel Phytoplasma taxon associated with jujube witches broom disease
International Journal of Systematic and Evolutionary Microbiology, 2003Co-Authors: Heeyoung Jung, T Sawayanagi, Shigeyuki Kakizawa, Hisashi Nishigawa, Shinichi Miyata, Kenro Oshima, Masashi Ugaki, Tadaaki Hibi, Shigetou NambaAbstract:Phylogenetic relationships of five jujube witches'-broom (JWB) Phytoplasma isolates from four different districts, and other Phytoplasmas, were investigated by 16S rDNA PCR amplification and sequence analysis. The 16S rDNA sequences of any pair of the five isolates of JWB Phytoplasmas were >99·5 % similar. The JWB Phytoplasma 16S rDNA sequences were most closely related to that of the elm yellows (EY) Phytoplasma in 16S-group VIII. Phylogenetic analysis of the 16S rDNA sequences from the JWB Phytoplasma isolates, together with sequences from most of the Phytoplasmas archived in GenBank, produced a tree in which the JWB isolates clustered as a discrete subgroup. The uniqueness of the JWB Phytoplasma appears to be correlated with a specific insect vector (Hishimonus sellatus) and the host plant (Zizyphus jujuba), or with a specific geographical distribution. The unique properties of the JWB Phytoplasma sequences clearly indicate that it represents a novel taxon, ‘Candidatus Phytoplasma ziziphi’.
Carmine Marcone - One of the best experts on this subject based on the ideXlab platform.
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Phytoplasma Diseases of Medicinal Crops
Phytoplasmas: Plant Pathogenic Bacteria - I, 2018Co-Authors: Carmine Marcone, Maria Grazia Bellardi, MadhupriyaAbstract:Phytoplasma diseases of medicinal plants occur worldwide and are of great concern. So far 19 different Phytoplasma ribosomal groups encompassing various subgroups have been reported. The subgroup 16SrI-B Phytoplasmas are the prevalent agents mainly detected in Europe, North America and Asia. Phytoplasma diseases of medicinal plants severely reduce yield and quality of crops along with the longevity of the plants. Changes in the composition of secondary metabolites are induced, while the levels of valuable phytochemicals are greatly affected. In contrast, an accumulation of pharmaceutically important compounds such as vinblastine and vincristine is reported in periwinkle upon Phytoplasma infections. Important Phytoplasma diseases of several medicinal plants with special reference to their impact on active biological constituents and secondary metabolites are reviewed. General information on geographic distribution, diagnostics, genetic diversity, natural transmission and management aspects of Phytoplasmas infecting medicinal plants are also discussed.
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Phytoplasma DISEASES OF MEDICINAL AND AROMATIC PLANTS
Journal of Plant Pathology, 2016Co-Authors: Carmine Marcone, Maria Grazia Bellardi, Assunta BertacciniAbstract:Medicinal and aromatic plants include a broad array of wild and cultivated plants which contain many biologically-active compounds, known as phytochemicals, that are of great interest for their ability to promote human and animal health. The present review provides a literature overview of Phytoplasma diseases affecting medicinal and aromatic plants, with an emphasis on Phytoplasma taxa associated. An overview of studies that examined the effect of Phytoplasma infections on phytochemical content and other secondary metabolites of affected plants is also included. Phytoplasma diseases of medicinal and aromatic plants occur worldwide; however, the majority of reports are from Europe and southeastern Asian countries. These diseases affect plant species belonging to over 70 families, mostly to Apiaceae and Asteraceae. They differ considerably in geographic distribution and size of the various taxonomic groups and subgroups of the associated Phytoplasmas. Subgroup 16SrI-B Phytoplasmas are the prevalent agents occurring mainly in Europe, North America and Asia. Phytoplasma presence induces changes in the amount and composition of secondary metabolites in diseased plants in which, however, the concentrations of valuable phytochemicals are greatly affected. An exception is represented by Phytoplasma diseases of periwinkle in which an accumulation of pharmaceutically important compounds occurs upon Phytoplasma infections. Prospects for future research are identified and critically discussed as well.
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Current status of Phytoplasma diseases of peach
Acta Horticulturae, 2015Co-Authors: Carmine MarconeAbstract:Peach (Prunus persica) is in many countries severely affected by yellows and decline diseases of Phytoplasmal etiology. These diseases are caused by phylogenetically different Phytoplasmas. X-disease is one of the most serious diseases of peach. It is widespread in North America and has not been observed elsewhere. This disease is induced by a distinct Phytoplasma, the X-disease agent âCandidatus Phytoplasma pruniâ, which is a member of the X-disease Phytoplasma group or 16SrIII group, subgroup 16SrIII-A. âCa. P. pruniâ is, at the level of 16S rDNA sequences, a homogeneous pathogen. Peach rosette, peach red suture, and peach yellows, also called little peach, are three other diseases which are mainly known from eastern North America. These diseases are currently of minor importance. They are also caused by the X-disease Phytoplasma. Peach yellow leaf roll (PYLR) is a major disease of peach that occurs in California. The causative agent, the PYLR Phytoplasma, is a member of the apple proliferation (AP) group and is most closely related to the pear decline Phytoplasma. In Europe, peach is affected by an economically important disorder known as European stone fruit yellows. This disorder is induced by âCa. P. prunorumâ which is a member of the AP group, subgroup 16SrX-B. âCa. P. prunorumâ is closely related to other important temperate fruit tree Phytoplasmas including the PYLR agent. In Lebanon and Iran, peach is affected by almond witchesâ-broom, a lethal disease that is induced by âCa. P. phoeniciumâ. This Phytoplasma is a member of the 16SrIX group, subgroup 16SrIX-B. Phytoplasmas of other phylogenetic groups, which are known to infect a wide range of plant hosts, have been identified in declining peach trees in several fruit growing areas worldwide. However, the pathological relevance of these non-peach Phytoplasmas needs to be investigated in many cases.
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Molecular biology and pathogenicity of Phytoplasmas
Annals of Applied Biology, 2014Co-Authors: Carmine MarconeAbstract:Phytoplasmas are a large group of plant-pathogenic wall-less, non-helical, bacteria associated with diseases, collectively referred to as yellows diseases, in more than a thousand plant species worldwide. Many of these diseases are of great economic importance. Phytoplasmas are difficult to study, in particular because all attempts at culturing these plant pathogens under axenic conditions have failed. With the introduction of molecular methods into phytoplasmology about two decades ago, the genetic diversity of Phytoplasmas could be elucidated and a system for their taxonomic classification based on phylogenetic traits established. In addition, a wealth of information was generated on Phytoplasma ecology and genomics, Phytoplasma–plant host interactions and Phytoplasma–insect vector relationships. Taxonomically, Phytoplasmas are placed in the class Mollicutes, closely related to acholeplasmas, and are currently classified within the provisional genus ‘Candidatus Phytoplasma’ based primarily on 16S rDNA sequence analysis. Phytoplasmas are characterised by a small genome. The sizes vary considerably, ranging from 530 to 1350 kilobases (kb), with overlapping values between the various taxonomic groups and subgroups, resembling in this respect the culturable mollicutes. The smallest chromosome, about 530 kb, is known to occur in the Bermuda grass white leaf agent ‘Ca. Phytoplasma cynodontis’. This value represents the smallest mollicute chromosome reported to date. In diseased plants, Phytoplasmas reside almost exclusively in the phloem sieve tube elements and are transmitted from plant to plant by phloem-feeding homopteran insects, mainly leafhoppers and planthoppers, and less frequently psyllids. Most of the Phytoplasma host plants are angiosperms in which a wide range of specific and non-specific symptoms are induced. Phytoplasmas have a unique and complex life cycle that involves colonisation of different environments, the plant phloem and various organs of the insect vectors. Furthermore, many Phytoplasmas have an extremely wide plant host range. The dynamic architecture of Phytoplasma genomes, due to the occurrence of repetitive elements of various types, may account for variation in their genome size and adaptation of Phytoplasmas to the diverse environments of their plant and insect hosts. The availability of five complete Phytoplasma genome sequences has made it possible to identify a considerable number of genes that are likely to play major roles in Phytoplasma–host interactions. Among these, there are genes encoding surface membrane proteins and effector proteins. Also, it has been shown that Phytoplasmas dramatically alter their gene expression upon switching between plant and insect hosts.
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'Candidatus Phytoplasma convolvuli', a new Phytoplasma taxon associated with bindweed yellows in four European countries.
International Journal of Systematic and Evolutionary Microbiology, 2012Co-Authors: Marta Martini, Assunta Bertaccini, Carmine Marcone, J. Mitrovic, Michael Maixner, D. Delic, Arben Myrta, Paolo Ermacora, Bojan DudukAbstract:Plants of Convolvulus arvensis exhibiting symptoms of undersized leaves, shoot proliferation and yellowing, collectively defined as bindweed yellows, were sampled in different regions of Europe and assessed for Phytoplasma infection by PCR amplification using Phytoplasma universal rRNA operon primer pairs. Positive results were obtained for all diseased plants. RFLP analysis of amplicons comprising the16S rRNA gene alone or the16S rRNA gene and 16-23S intergenic spacer region indicated that the detected Phytoplasmas were distinguishable from all other previously described rRNA gene sequences. Analysis of 16S rRNA gene sequences derived from seven selected Phytoplasma strains (BY-S57/11, BY-S62/11, BY-I1015, BY-I1016, BY-BH1, BY-BH2 and BY-G) showed that they were nearly identical (99.9–100 % gene sequence similarity) but shared less than 97.5 % similarity with comparable sequences of other Phytoplasmas. Thus, BY Phytoplasmas represent a new taxon whose closest relatives are stolbur Phytoplasma strains and ‘ Candidatus Phytoplasma fragariae ’ with which they share 97.2 % and 97.1 % 16S rRNA gene sequence similarity, respectively. Phylogenetic analysis of 16S rRNA gene sequences confirmed that bindweed yellows Phytoplasma strains collectively represent a distinct lineage within the Phytoplasma clade and share a common ancestor with previously published or proposed ‘Candidatus Phytoplasma’ taxa within a major branch including aster yellows and stolbur Phytoplasmas. On the basis of unique 16S rRNA gene sequences and biological properties that include a single host plant species and a geographical distribution limited to parts of Europe, the bindweed yellows (BY) Phytoplasmas represent a coherent but discrete taxon, ‘Candidatus Phytoplasma convolvuli’, with strain BY-S57/11 (GenBank accession no. JN833705) as the reference strain.
