Submitted to: Phytoplasmas: Genomes, Plant Hosts and Vectors
Publication Type: Book / Chapter
Publication Acceptance Date: 4/29/2009
Publication Date: 1/15/2010
Citation: Lee, I., Zhao, Y., Davis, R.E. 2010. Prospect of multiple gene-based systems for differentiation and classification of phytoplasmas. In: Weintraub, P., Jones, P., editors. Phytoplasmas: Genomes, Plant Hosts and Vectors. Wallingford, UK: CABI Publishing. p. 51-63.
Technical Abstract: During the last two decades, over 800 phytoplasma strains associated with several hundred plant diseases and numerous insect vectors have been identified. Research has yielded new knowledge about phytoplasma ecology and phylogenetic relationships. A taxonomic system has emerged, and perspectives on phytoplasma speciation have changed. Guidelines for naming new ‘Candidatus Phytoplasma’ species, employing the 16S rRNA gene as the sole phylogenetic marker for species delineation were proposed and to date, 26 ‘Ca. Phytoplasma’ species have been named, forming the core framework of the emerging phytoplasma taxonomy. Because of its highly conserved nature, the 16S rRNA gene cannot be used for delineation of many closely related but distinct biological and ecological strains that are important for epidemiological studies of phytoplasmal diseases. Additional molecular markers are much needed for finer differentiation of phytoplasmas. The concept of multi-gene sequence analysis for a comprehensive differentiation of phytoplasmas into species as well as strains is emerging. Combined analyses employing the 16S rRNA gene and one or more less conserved molecular markers could compensate for the deficiency of the 16S rRNA based classification system.