33 research outputs found
‘Candidatus Phytoplasma asteris’, a novel phytoplasma taxon associated with aster yellows and related diseases.
Aster yellows (AY) group (16SrI) phytoplasmas are associated with over 100 economically
important diseases worldwide and represent the most diverse and widespread phytoplasma
group. Strains that belong to the AY group form a phylogenetically discrete subclade within the
phytoplasma clade and are related most closely to the stolbur phytoplasma subclade, based on
analysis of 16S rRNA gene sequences. AY subclade strains are related more closely to their
culturable relatives, Acholeplasma spp., than any other phytoplasmas known. Within the AY
subclade, six distinct phylogenetic lineages were revealed. Congruent phylogenies obtained by
analyses of tuf gene and ribosomal protein (rp) operon gene sequences further resolved the
diversity among AY group phytoplasmas. Distinct phylogenetic lineages were identified by RFLP
analysis of 16S rRNA, tuf or rp gene sequences. Ten subgroups were differentiated, based on
analysis of rp gene sequences. It is proposed that AY group phytoplasmas represent at least one
novel taxon. Strain OAY, which is a member of subgroups 16SrI-B, rpI-B and tufI-B and is
associated with evening primrose (Oenothera hookeri ) virescence in Michigan, USA, was selected
as the reference strain for the novel taxon ‘Candidatus Phytoplasma asteris’. A comprehensive
database of diverse AY phytoplasma strains and their geographical distribution is presented