Schneider, Bernd


Publications (12)

Revision of the ‘Candidatus Phytoplasma’ species description guidelines

Citation
Bertaccini et al. (2022). International Journal of Systematic and Evolutionary Microbiology 72 (4)
Names
Ca. Phytoplasma
Subjects
Ecology, Evolution, Behavior and Systematics General Medicine Microbiology
Abstract
The genus ‘Candidatus Phytoplasma’ was proposed to accommodate cell wall-less bacteria that are molecularly and biochemically incompletely characterized, and colonize plant phloem and insect vector tissues. This provisional classification is highly relevant due to its application in epidemiological and ecological studies, mainly aimed at keeping the severe phytoplasma plant diseases under control worldwide. Given the increasing discovery of molecular diversity within the genus ‘Ca. Phytoplasma’, the proposed guidelines were revised and clarified to accommodate those ‘Ca. Phytoplasma’ species strains sharing >98.65 % sequence identity of their full or nearly full 16S rRNA gene sequences, obtained with at least twofold coverage of the sequence, compared with those of the reference strain of such species. Strains sharing <98.65 % sequence identity with the reference strain but >98.65 % with other strain(s) within the same ‘Ca. Phytoplasma’ species should be considered related strains to that ‘Ca. Phytoplasma’ species. The guidelines herein, keep the original published reference strains. However, to improve ‘Ca. Phytoplasma’ species assignment, complementary strains are suggested as an alternative to the reference strains. This will be implemented when only a partial 16S rRNA gene and/or a few other genes have been sequenced, or the strain is no longer available for further molecular characterization. Lists of ‘Ca. Phytoplasma’ species and alternative reference strains described are reported. For new ‘Ca. Phytoplasma’ species that will be assigned with identity ≥98.65 % of their 16S rRNA gene sequences, a threshold of 95 % genome-wide average nucleotide identity is suggested. When the whole genome sequences are unavailable, two among conserved housekeeping genes could be used. There are 49 officially published ‘Candidatus Phytoplasma’ species, including ‘Ca. P. cocostanzaniae’ and ‘Ca. P. palmae’ described in this manuscript.

Widespread occurrence of ‘Candidatus Phytoplasma ulmi’ in elm species in Germany

Citation
Schneider et al. (2020). BMC Microbiology 20 (1)
Names
Ca. Phytoplasma ulmi
Subjects
Microbiology Microbiology (medical)
Abstract
Abstract Background ‘Candidatus Phytoplasma ulmi’ is the agent associated with elm yellows and has been categorised in the European Union as a quarantine pathogen. For central and northern European countries, information on the occurrence and distribution of the pathogen and its impact on elms is scarce, so a survey of native elm trees has been conducted in Germany. Results About 6500 samples from Ulmus minor, Ulmus laevis and Ulmus glabra, were collected nationwide. Phytoplasma detection was performed by applying a universal 16Sr DNA-based quantitative PCR (qPCR) assay and a novel ‘Ca. P. ulmi’ specific qPCR assay targeting the 16S–23S spacer region. Both assays revealed that 28% of the samples were infected by ‘Ca. P. ulmi’, but infection rates of the elm species and regional incidences differed. The phytoplasma presence in the trees was not correlated to disease-specific symptoms. The survey identified a regional disparity of infection which was high in east, south and central Germany, whereas only a few infected sites were found in the western and northern parts of the country. Monitoring the seasonal titre of ‘Ca. P. ulmi’ in an infected tree by qPCR revealed a high colonisation in all parts of the tree throughout the year. Conclusions ‘Ca. P. ulmi’ is widely present in elms in Germany. The rare occurrence of symptoms indicates either a high degree of tolerance in elm populations or a low virulence of pathogen strains enabling high infection rates in a long-living host.

Widespread occurrence of 'Candidatus Phytoplasma ulmi' in elm species in Germany

Citation
Schneider et al. [posted content, 2020]
Names
Ca. Phytoplasma ulmi
Abstract
Abstract Background: Candidatus Phytoplasma ulmi' is the agent associated with elm yellows and has been categorised in the European Union as a quarantine pathogen. For central and northern European countries, information on the occurrence and distribution of the pathogen and its impact on elms is scarce, so a survey of native elm trees has been conducted in Germany. Results: About 6,500 samples from Ulmus minor , Ulmus laevis and Ulmus glabra , were collected nationwide. Phytoplasma detection was performed by applying a universal 16Sr DNA-based quantitative PCR (qPCR) assay and a novel ' Ca. P. ulmi' specific qPCR assay targeting the 16S-23S spacer region. Both assays revealed that 28% of the samples were infected by ‘ Ca. P. ulmi’, but infection rates of the elm species and regional incidences differed. The phytoplasma presence in the trees was not correlated to disease-specific symptoms. The survey identified a regional disparity of infection which was high in east, south and central Germany, whereas only a few infected sites were found in the western and northern parts of the country. Monitoring the seasonal titre of ‘Ca. P. ulmi’ in an infected tree by qPCR revealed a high colonisation in all parts of the tree throughout the year. Conclusions: ‘ Ca. P. ulmi’ is widely present in elms in Germany. The rare occurrence of symptoms indicates either a high degree of tolerance in elm populations or a low virulence of pathogen strains enabling high infection rates in a long-living host.

Widespread occurrence of Candidatus Phytoplasma ulmi infecting elm species in Germany

Citation
Schneider et al. [posted content, 2020]
Names
Ca. Phytoplasma ulmi
Abstract
Abstract Background: Candidatus Phytoplasma ulmi is the causative agent of elm yellows and has been categorised in the European Union as a quarantine pathogen in the past. For central and northern European countries, information on the occurrence and distribution of the pathogen and its impact on elms is scarce, so a survey of native elm trees has been conducted in Germany. Results: About 6,500 samples in total, from Ulmus minor , Ulmus laevis and Ulmus glabra , were collected nationwide. Phytoplasma detection was performed by applying a universal 16Sr DNA-based real-time PCR assay and a novel Ca . P. ulmi species-specific real-time PCR assay targeting the 16S-23S spacer region. Both assays revealed that 28% of the samples were infected by Ca . P. ulmi, but infection rates of the elm species and regional incidences differed. The infection of trees is not correlated to disease-specific symptoms. The survey identified a regional disparity of infection which was high in east, south and central Germany, whereas only a few infected sites were found in the western and northern parts of the country. No correlation was apparent between altitude level and the prevalence of infection. First insights into the monitoring of the seasonal titre of Ca . P. ulmi in an infected tree by real-time PCR revealed high colonisation in all parts of the tree throughout the year. Conclusions: Ca . P. ulmi-infection is widely present in elms in Germany. The rare occurrence of symptoms indicates either a high degree of tolerance in elm populations or a low virulence of pathogen strains enabling high infection rates in a long-living host.

Draft Genome Sequence of “ Candidatus Phytoplasma oryzae” Strain Mbita1, the Causative Agent of Napier Grass Stunt Disease in Kenya

Citation
Fischer et al. (2016). Genome Announcements 4 (2)
Names
Ca. Phytoplasma oryzae
Subjects
Genetics Molecular Biology
Abstract
ABSTRACT Phytoplasmas are bacterial plant pathogens with devastating impact on agricultural production worldwide. In eastern Africa, Napier grass stunt disease causes serious economic losses in the smallholder dairy industry. This draft genome sequence of “ Candidatus Phytoplasma oryzae” strain Mbita1 provides insight into its genomic organization and the molecular basis of pathogenicity.

‘Candidatus Phytoplasma pini’, a novel taxon from Pinus silvestris and Pinus halepensis

Citation
Schneider et al. (2005). International Journal of Systematic and Evolutionary Microbiology 55 (1)
Names
Ca. Phytoplasma pini
Subjects
Ecology, Evolution, Behavior and Systematics General Medicine Microbiology
Abstract
Pinus silvestris and Pinus halepensis trees grown in Germany and Spain, respectively, showing abnormal shoot branching, dwarfed needles and other symptoms were examined for the presence of plant-pathogenic mollicutes (phytoplasmas). While phytoplasmas could not be detected unambiguously with microscopical methods, PCR amplification using universal phytoplasma primers yielded positive results. Samples collected from symptomatic and non-symptomatic plant parts of both symptomatic Pinus silvestris and Pinus halepensis trees tested positive. Also, surrounding non-symptomatic trees proved to be phytoplasma-infected. Comparisons revealed that the 16S rRNA gene sequences of the phytoplasmas identified in Pinus silvestris and Pinus halepensis were nearly identical. However, the pine phytoplasma is only distantly related to other phytoplasmas. The closest relatives are members of the palm lethal yellowing and rice yellow dwarf groups and ‘Candidatus Phytoplasma castaneae’, which share between 94·5 and 96·6 % 16S rRNA gene sequence similarity. From these data it can be concluded that the phytoplasmas identified in the two Pinus species represent a coherent but discrete taxon; it is proposed that this taxon be distinguished at putative species level under the name ‘Candidatus Phytoplasma pini’.