Lee I-M, Gundersen-Rindal D E, Davis R E, Bottner K D, Marcone C, Seemüller E
USDA-ARS Molecular Plant Pathology Laboratory, Beltsville, MD 20705, USA.
Insect Biocontrol Laboratory, Beltsville, MD 20705, USA.
Int J Syst Evol Microbiol. 2004 Jul;54(Pt 4):1037-1048. doi: 10.1099/ijs.0.02843-0.
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.
翠菊黄化组（16SrI）植原体与全球100多种具有重要经济意义的病害相关，是种类最多、分布最广的植原体组。基于16S rRNA基因序列分析，属于翠菊黄化组的菌株在植原体进化枝内形成一个系统发育上离散的亚分支，与 stolbur 植原体亚分支关系最为密切。与其他已知植原体相比，翠菊黄化亚分支菌株与其可培养的近缘种无胆甾原体属的亲缘关系更近。在翠菊黄化亚分支内，揭示了六个不同的系统发育谱系。通过对tuf基因和核糖体蛋白（rp）操纵子基因序列的分析获得的一致系统发育进一步解析了翠菊黄化组植原体之间的多样性。通过对16S rRNA、tuf或rp基因序列的RFLP分析鉴定出不同的系统发育谱系。基于rp基因序列分析，区分出了十个亚组。有人提出翠菊黄化组植原体至少代表一个新的分类单元。菌株OAY属于16SrI-B、rpI-B和tufI-B亚组，与美国密歇根州的月见草（Oenothera hookeri）变绿有关，被选为新分类单元“‘Ca. Phytoplasma asteris’”的参考菌株。本文还展示了一个包含多种翠菊黄化植原体菌株及其地理分布的综合数据库。
