Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 11, 2002
Publication Date: N/A
Interpretive Summary: Phytoplasmas are minute, cell wall-less bacterial pathogens that cause diseases in hundreds of plants species worldwide. Numerous destructive phytoplasmas are presently limited in geographic distribution, are potential invasive species, and are of quarantine/phytosanitary concern. It is important to ascertain their identities and to develop means for their rapid detection and identification in order to facilitate quarantines to prevent their introduction into new regions. Since it is not possible to isolate any phytoplasma in pure culture, characteristics that are commonly used for detection, identification, and classification of other bacteria cannot be used with phytoplasmas. In this study, a previously undescribed phytoplasma was discovered in diseased plants of Erigeron and Catharanthus growing in Brazil. Through the use of DNA-based methods, this phytoplasma was found to be closely related to, but distinct from, ash yellows phytoplasma, Candidatus Phytoplasma fraxini', which has been decribed previously only in North America. This work characterizes the erigeron phytoplasma as representative of a new phytoplasmal evolutionary lineage, and provides molecular markers whereby the phytoplasma may be detected and identified, facilitating studies in epidemiology and disease control, and efforts in plant quarantine. The findings will interest scientists, plant disease diagnosticians, and plant quarantine/phytosanitary agencies involved in fundamental studies, detection and diagnosis of plant diseases, and interception of exotic pathogens in regional and international movement of germplasm and plant products.
A previously undescribed phytoplasma, erigeron witches' broom phytoplasma, was detected in diseased plants of Erigeron sp. and Catharanthus roseus exhibiting symptoms of witches' broom and chlorosis in the state of Sao Paulo, Brazil. On the basis of restriction fragment length polymorphism (RFLP) analysis of 16S rDNA amplified in the polymerase chain reaction (PCR), erigeron witches' broom phytoplasma was classified in group 16SrVII (ash yellows phytoplasma group), new subgroup VII-B. Phylogenetic analysis of 16S rDNA sequences indicated that EriWB phytoplasma represents a new lineage that is distinct from that of described strains of ash yellows phytoplasma. Erigeron witches' broom phytoplasma is the first member of the ash yellows phytoplasma group to be recorded in Brazil.