Phytoplasmas are bacterial pathogens that pose a threat to cereal and vegetable production worldwide. However, there is limited information regarding the occurrences of phytoplasmas in Central Europe. In this study we examined samples taken from crop and ornamental plants showing symptoms indicative of phytoplasma infection. Phytoplasmas related to 'Candidatus Phytoplasma asteris' were detected in eight plant species (carrot, lupine, pea, cauliflower, mustard, maize, juniper and marigold). Based on the restriction fragment length polymorphism analysis of the 16S rDNA, the phytoplasmas were classified as subgroup 16SrI-B, 16SrI-L or a complex strain, which harboured the I-B and I-L-type 16S rRNA genes. Individual 16S rDNA sequences were analysed from those heterogeneous strains and as many as five genetic variants were distinguished. By operon-specific amplification of the 16S rRNA genes with primers complementary to RP166 phytoplasma genome, we detected 16SrI-L/B phytoplasma strains in the multivariant samples. The I-L-type sequences were amplified from rrnA and the I-B-type sequences were amplified from rrnB. Molecular phylogeny based on the 16S rRNA showed that all the detected phytoplasma variants were clustered with a 'Ca. Phytoplasma asteris' subclade and were closely related to the 16SrI-B subgroup. Despite the variability of 16S rDNA, the strains from all the eight crops shared identical tuf gene sequences. We report, for the first time, 16SrI-B phytoplasma infecting lupine, field pea, cauliflower and mustard, 16SrI-L phytoplasma infecting maize and field pea and 16SrI-L/B phytoplasma infecting carrot, lupine and marigold. We further demonstrate variability in the 16S rRNA genes found in the 16SrI-B-related phytoplasma genomes worldwide. For clearer and more unambiguous nomenclature, we propose that in the future, the more intuitive subgroup 16SrI-L/B be used for heterogenic phytoplasma strains instead of 16SrI-(B/L)L.

中文翻译：

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在 16SrI-B 相关植物病原植原体菌株中发现的 16S rRNA 基因之间的基因组内和外变异

植原体是一种细菌病原体，对全世界的谷物和蔬菜生产构成威胁。然而，关于中欧植原体发生的信息有限。在这项研究中，我们检查了从作物和观赏植物中采集的样本，这些样本显示出表明植原体感染的症状。与' Candidatus相关的植原体在八种植物（胡萝卜、羽扇豆、豌豆、花椰菜、芥末、玉米、杜松和万寿菊）中检测到了星状植原体。基于16S rDNA的限制性片段长度多态性分析，植原体被归类为亚群16SrI-B、16SrI-L或含有IB和IL型16S rRNA基因的复杂菌株。从这些异质菌株中分析了单个 16S rDNA 序列，并区分了多达五种遗传变异。通过使用与 RP166 植原体基因组互补的引物对 16S rRNA 基因进行操纵子特异性扩增，我们在多变体样品中检测到 16SrI-L/B 植原体菌株。从rrnA扩增IL型序列，从rrnB扩增IB型序列。钙。Phytoplasma asteris' subclade 与 16SrI-B 亚群密切相关。尽管 16S rDNA 存在变异性，但来自所有八种作物的菌株具有相同的tuf基因序列。我们首次报道了 16SrI-B 植原体感染羽扇豆、豌豆、花椰菜和芥菜，16SrI-L 植原体感染玉米和豌豆，16SrI-L/B 植原体感染胡萝卜、羽扇豆和万寿菊。我们进一步证明了在全球 16SrI-B 相关植原体基因组中发现的 16S rRNA 基因的变异性。为了更清晰、更明确的命名，我们建议在未来，更直观的亚组 16SrI-L/B 用于异源植原体菌株，而不是 16SrI-(B/L)L。