Histopathology and Within-Plant Distribution of the Phytoplasma Associated with Australian Papaya Dieback

Siddique, Aisha; Guthrie, J. N.; Walsh, Kerry B.; White, Daniel T.; Scott, Paul T.

doi:10.1094/pdis.1998.82.10.1112

Cited by 55 publications

(29 citation statements)

References 21 publications

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“…No such types of structures were observed in healthy plants. The observation of pleomorphic forms of phytoplasma in the infected cells is in agreement with previous reports (Siddique et al., 1998, 2001). The polymerase chain reaction (PCR) results showed an amplified product of the predicted size (1.67 kb; Fig.…”

Section: Resultssupporting

confidence: 93%

Phytoplasma Association with Gerbera Phyllody in Australia

Siddique¹

2005

Journal of Phytopathology

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Gerbera (Gerbera jamesonii L.) plants with phyllody symptoms (green flower) were observed in Central Queensland, Australia. Leaves and flowers from both symptomatic and asymptomatic healthy plants were examined by transmission electron microscopy (TEM). The presence of pleomorphic bodies similar to phytoplasma was observed exclusively in diseased plants. Polymerase chain reaction (PCR) with phytoplasmaspecific primers confirmed the presence of phytoplasma DNA in the infected plants. Further DNA sequencing analysis of the PCR product revealed high homology with other phytoplasma DNA in the database. Based on phylogenetic analysis of 16S rRNA the gerbera phyllody phytoplasma was grouped under Peanut witchesÕ broom as described by Lee et al. (1998). The results of TEM, PCR and sequencing analysis clearly indicate phytoplasmal association with phyllody disease of gerbera.

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Section: Resultssupporting

confidence: 93%

Phytoplasma Association with Gerbera Phyllody in Australia

Siddique¹

2005

Journal of Phytopathology

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“…It has been observed in our laboratory that alfalfa inoculated through dodder transmission by 16SrI-B, though showing symptoms of infection (leaf curling, yellowing), was not positive in leaf material using nested PCR until 2 weeks after symptom expression began (R. Alleman, unpublished data). Symptom expression and detection are often very difficult to reconcile in many hosts, adding to the difficulty of studying these organisms (Gibb et al 1999;Markham 1982;Siddique et al 1998).…”

Section: Discussionmentioning

confidence: 99%

Identification of aster yellows phytoplasmas in soybean in Wisconsin based on RFLP analysis of PCR-amplified products (16S rDNAs)

Lee

Grau

Lukaesko

et al. 2002

Canadian Journal of Plant Pathology

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Phytoplasmas have been detected for the first time by molecular methods in soybeans in Wisconsin. Nested polymerase chain reaction (PCR) using a combination of two phytoplasma-specific "universal" primer pairs (P1/P7-R16F2n/R16R2 and R16mF2/R16mR1-R16F2n/R16R2) amplified 16S rDNA (with expected fragment size of 1.2 kilobases) in soybean leaf tissue in 48 of 121 plants tested. Restriction fragment length polymorphism analysis of nested PCR products indicated that only 2 of these samples contained phytoplasmas. Gram-positive bacterial 16S rDNA genes were detected in 46 PCR positive samples. This was confirmed by culturing bacteria and direct PCR of soybean seed. In the two soybean samples, phytoplasmas belonging to the aster yellows phytoplasma group (16SrI), subgroup 16SrI-A, and a newly established subgroup, 16SrI-O, were identified. Phylogenetic analysis using partial 16S rDNA sequences (1.2 kilobases) from representative phytoplasma strains clustered soybean phytoplasmas into two distinct phylogenetic lineages that are consistent with the two subgroups defined by restriction fragment length polymorphism analysis. No correlation between the presence of phytoplasmas and the occurrence of "green-stem syndrome" in soybeans in Wisconsin was detected.Résumé : Des phytoplasmes ont été détectés pour la première fois par méthodes moléculaires dans le soja au Wisconsin. La réaction en chaîne de la polymérase (RCP) nichée utilisant une combinaison de deux paires d'amorces « universelles » spécifiques aux phytoplasmes (P1/P7-R16F2n/R16R2 et R16mF2/R16mR1-R16F2n/R16R2) a amplifié de l'ADNr 16S (avec fragment prévu de 1,2 kilobases) provenant de tissu foliaire de soja de 48 des 121 plantes testées. L'analyse du polymorphisme de la longueur des fragments de restriction des produits de la RCP nichée a montré que seulement 2 de ces échantillons contenaient des phytoplasmes. Des gènes d'ADNr 16S de bactéries grampositives ont été détectés dans 46 échantillons de RCP positifs. Une confirmation a été obtenue par culture de bactéries et RCP directe avec des graines de soja. Dans les deux échantillons de soja, des phytoplasmes appartenant au groupe du phytoplasme de la jaunisse de l'aster (16SrI), sous-groupe 16SrI-A, et un nouveau sous-groupe, 16SrI-O, ont été identifiés. L'analyse phylogénétique avec des portions de séquences d'ADNr 16S (1,2 kilobases) de souches représentatives de phytoplasmes a permis de classer les phytoplasmes de soja en deux lignées phylogénétiques distinctes compatibles avec les deux sous-groupes trouvés par l'analyse du polymorphisme de la longueur du fragment de restriction. La présence des phytoplasmes n'était pas corrélée à celle du « syndrome de la tige verte » du soja au Wisconsin.Mots clés : phytoplasme, Glycine max, jaunisse de l'aster, réaction en chaîne de la polymérase, polymorphisme de la longueur du fragment de restriction.Lee et al.: soybean / aster yellows phytoplasma / identification 130

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“…However, PCR assays indicated the presence of the phytoplasma DNA in these tissues. Variations in the results of PCR assay and electron microscopy may possibly be due to low concentrations and irregular distribution of PDB phytoplasma in infected plants (Siddique et al 1998).…”

Section: Polymerase Chain Reaction-based Assaysmentioning

confidence: 99%

Detection of Bacterial and Phytoplasmal Pathogens

Narayanasamy¹

2010

Microbial Plant Pathogens-Detection and Disease Diagnosis:

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Bacterial pathogens classified as prokaryotes are much simpler in structure and smaller in size and they have less complex structural features compared to fungal plant pathogens. As the morphological characteristics of bacterial cells are less variable, biological, biochemical, physiological, immunological and genomic characteristics have to be determined for reliable identification and meaningful classification of bacterial pathogens. Detection and identification of bacterial plant pathogens present in whole plants and in propagative plant materials have been possible by employing isolation on cultural media and metabolic fingerprinting methods. But they are labor-intensive and require long time. Results often are inconclusive. Isozyme analysis, direct colony thin layer chromatography and gel electrophoresis techniques have been successfully applied for the detection of some bacterial pathogens. Immunoassays and nucleic acid-based assays have become widely accepted techniques, providing more sensitive and specific detection and quantification of bacterial pathogens affecting a wide range of host plant species. However, the major limitation of the molecular techniques is their inability to discriminate living cells from the dead ones. Attempts have been made to overcome this limiting factor by using DNA binding dyes and estimating pathogen RNAs as an indicator of cell viability. The diagnostic methods have both merits and demerits and hence, appropriate method has to be selected based on cost-effectiveness and possibility of obtaining reliable results rapidly to suit the requirements of the investigation concerned.Phytoplasmas are cell wall-less, nonculturable bacteria belonging to Mollicutes. Lack of cultural characteristics has made obligatory to study the morphological characteristics of phytoplasmas present in the phloem cells of infected plant hosts by observing under electron microscopes. As most of the phytoplasmas look alike in the ultrathin sections, the morphological characters have no diagnostic value. Histochemical methods using DNA binding dyes have been employed to localize the phytoplasmas in the host cells. Application of immunoassays and nucleic acidbased techniques has been effective in providing information for the identification and differentiation of phytoplasams. Polyclonal and monoclonal antibodies have been generated for detection of phytoplasmas infecting several plant species. Universal and species-specific primers and probes have been designed based on

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Histopathology and Within-Plant Distribution of the Phytoplasma Associated with Australian Papaya Dieback

Cited by 55 publications

References 21 publications

Phytoplasma Association with Gerbera Phyllody in Australia

Phytoplasma Association with Gerbera Phyllody in Australia

Identification of aster yellows phytoplasmas in soybean in Wisconsin based on RFLP analysis of PCR-amplified products (16S rDNAs)

Detection of Bacterial and Phytoplasmal Pathogens

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