The “Candidatus Phytoplasma” Concept: New Names but not yet a Taxonomy for the Fastidious Plant Pathogenic Mollicutes
The aetiology of what we now call phytoplasma diseases is perhaps the least understood in the history of plant pathology. Only in 1967 electron microscopy studies revealed that many diseases which were thought to be caused by viruses were actually associated with wall-less endo-cellular parasitic prokaryotic cells (reviewed in 1). Two different morphological types of wall-less prokaryotes were detected in plant phloem: the in vitro-cultivable helical-shaped wall-less prokaryotes were named spiroplasmas, while the non- helical pleomorphic forms that could not be cultivated in axenic media were simply called mycoplasma-like organisms (MLOs) as they resembled mycoplasmas on morphological grounds. Their early classification was based on the symptoms caused in the host and vector transmission characteristics (rev. in 1).
KeywordsAxenic Medium rRNA Operon Aster Yellow Mycoplasmalike Organism Plant Phloem
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