Phy.to.plas'ma. Gr. neut. n.phyton, a plant; Gr. neut. n.plasmasomething formed or molded, a form; N.L. neut. n.Phytoplasma, a form from a plant.Tenericutes / Mollicutes / Acholeplasmatales / Incertae Sedis ‐ Family II /CandidatusPhytoplasmaThe generic name ‘CandidatusPhytoplasma’ has been adopted by specialists to refer to a monophyletic clade of wall‐less phytopathogenic bacteria affiliated with the orderAcholeplasmatalesin the classMollicutes. 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.