CandidatusPhytoplasma

Abstract

Phy.to.plas'ma. Gr. neut. n. phyton , a plant; Gr. neut. n. plasma something formed or molded, a form; N.L. neut. n. Phytoplasma , a form from a plant. Tenericutes / Mollicutes / Acholeplasmatales / Incertae Sedis ‐ Family II / Candidatus Phytoplasma The generic name ‘ Candidatus Phytoplasma’ has been adopted by specialists to refer to a monophyletic clade of wall‐less phytopathogenic bacteria affiliated with the order Acholeplasmatales in the class Mollicutes . These small (<1 µm) pleomorphic cells occur within the nutritionally‐rich phloem sap and sieve elements of plants, and in the gut or hemolymph of insects that feed on plants. Sustained culture in cell‐free media has not yet been demonstrated for any phytoplasma, and a recent report of successful axenic culture remains to be independently replicated. Reference strains are maintained in plants by periodic graft inoculation. Sequence analysis of PCR‐amplified rDNA, plus considerations of the plant host range and vector species, provide a basis for phytoplasma strain identification and assignment to phylogenetic groups. Hundreds of plant species are susceptible to infection, with signs including discoloration, stunting, virescence, phyllody, proliferation of flowers or shoots, or sterility. The necessity for strict quarantine regulations to control the spread of phytoplasmas among important plants such as fruit trees, palms, and grapevines illustrates the importance of accurate identification and nomenclature for these organisms.

An online global database of Hemiptera -Phytoplasma-Plant biological interactions

“…For phytoplasmas, the classification follows the rules established by the International Code of Nomenclature of Prokaryotes (Parker et al 2015) and additional criteria established by the Phytoplasma/Spiroplasma Working Team (IRPCM, Phytoplasma/Spiroplasma Working Team - Phytoplasma Taxonomy Group 2004, Harrison et al 2018). All phytoplasma strains in the database are listed as Incertae sedis and they are classified into groups and subgroups defined based on restriction fragment length polymorphism (RFLP) analysis of Polymerase Chain Reaction (PCR)-amplified 16S rRNA gene fragments (Zhao et al 2010).…”

“…Phytoplasmas were observed for the first time in 1967 (Doi et al 1967) and only recently classified based on phylogenetic analysis of 16S rRNA and ribosomal protein (rp) gene sequences, revealing their diversity and phylogenetic position (Lee et al 2000; IRPCM, Phytoplasma/Spiroplasma Working Team - Phytoplasma Taxonomy Group 2004). To date, 33 groups and more than 120 subgroups have been recognised based on 16Sr genetic data and 44 taxa have been given the provisional taxonomic status of ‘ Candidatus ’ (Harrison et al 2018), denoting not-yet cultured bacteria. As phytoplasmas do not satisfy the four Koch postulates (i.e.…”