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Bertaccini A, Arocha-Rosete Y, Contaldo N, Duduk B, Fiore N, Montano HG, Kube M, Kuo CH, Martini M, Oshima K, Quaglino F, Schneider B, Wei W, Zamorano A. Revision of the ' Candidatus Phytoplasma' species description guidelines. Int J Syst Evol Microbiol 2022; 72. [PMID: 35471141 DOI: 10.1099/ijsem.0.005353] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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.
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Affiliation(s)
- Assunta Bertaccini
- Department of Agricultural and Food Sciences, Alma Mater Studiorum - University of Bologna, Bologna, Italy
| | | | - Nicoletta Contaldo
- Department of Agricultural and Food Sciences, Alma Mater Studiorum - University of Bologna, Bologna, Italy
| | - Bojan Duduk
- Institute of Pesticides and Environmental Protection, Belgrade, Serbia
| | - Nicola Fiore
- Faculty of Agricultural Sciences, Department of Plant Protection, University of Chile, Santiago, Chile
| | - Helena Guglielmi Montano
- Department of Entomology and Plant Pathology, Federal Rural University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Michael Kube
- Department of Integrative Infection Biology Crops-Livestock, University of Hohenheim, Stuttgart, Germany
| | - Chih-Horng Kuo
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan, ROC
| | - Marta Martini
- Department of Agricultural, Food, Environmental and Animal Sciences, University of Udine, Udine, Italy
| | - Kenro Oshima
- Faculty of Bioscience and Applied Chemistry, Department of Clinical Plant Science, Hosei University, Japan
| | - Fabio Quaglino
- Department of Agricultural and Environmental Sciences - Production, Landscape, Agroenergy, University of Milan, Milan, Italy
| | - Bernd Schneider
- Julius Kuehn-Institute, Federal Research Centre for Cultivated Plants, Institute for Plant Protection in Fruit Crops and Viticulture, Dossenheim, Germany
| | - Wei Wei
- Molecular Plant Pathology Laboratory, USDA/ARS, Beltsville, MD, USA
| | - Alan Zamorano
- Faculty of Agricultural Sciences, Department of Plant Protection, University of Chile, Santiago, Chile
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