The present study was performed to investigate root-associated bacteria from Platycodon grandiflorum, a medicinal plant commonly grown in East Asia. Isolates were obtained from the rhizosphere or root interior with various culture media, and phylogenetic analyses were performed based on their 16S rDNA sequences. In consideration of practical applications, traits related to plant growth promotion and niche adaptation were assessed in several endophytic strains with fewer biosafety concerns. The effects of a bacterial inoculation on seedling and mature plant growth were evaluated. Seventeen genera that encompassed more than 30 bacterial lineages were successfully retrieved from the roots, the majority of which have not been reported as P. grandiflorum-associated bacteria, particularly for non-negligible Proteobacteria. Although nitrogen-fixing or phosphate-solubilizing and indole acetic acid-producing activities were recorded in all of the strains selected, these strains were beneficial or detrimental to plant growth as evidenced by their influence on the length of seedlings and biomass of mature plants. Among the 4 endophytic Rhizobium species tested in the present study, the potentially novel Rhizobium sp. BF-E16, which was more compatible with the non-leguminous medicinal plant P. grandiflorum, was identified. Other than plant growth-promoting traits, characteristics such as plant constituent-hydrolyzing activities need to be taken into consideration and their roles clarified when investigating plant growth-promoting rhizobacteria.

中文翻译：

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药用植物桔梗根系细菌的探索

本研究旨在调查桔梗（一种常见于东亚的药用植物）中的根相关细菌。从根际或根内部用各种培养基获得分离株，并根据其 16S rDNA 序列进行系统发育分析。考虑到实际应用，在几个生物安全问题较少的内生菌株中评估了与植物生长促进和生态位适应相关的性状。评估了细菌接种对幼苗和成熟植物生长的影响。包含 30 多个细菌谱系的 17 个属被成功地从根中检索到，其中大部分尚未被报告为 P.grandiflorum 相关细菌，特别是对于不可忽略的变形菌。尽管在所有选择的菌株中都记录了固氮或溶磷以及产生吲哚乙酸的活性，但这些菌株对植物生长有益或有害，这通过它们对幼苗长度和成熟植物生物量的影响来证明。在本研究中测试的 4 种内生根瘤菌中，潜在的新型根瘤菌属。BF-E16 与非豆科药用植物 P.grandiflorum 更相容。除了促进植物生长的性状外，在研究促进植物生长的根际细菌时，还需要考虑植物成分水解活动等特征，并阐明它们的作用。这些菌株对植物生长有益或有害，这可以通过它们对幼苗长度和成熟植物生物量的影响来证明。在本研究中测试的 4 种内生根瘤菌中，潜在的新型根瘤菌属。BF-E16 与非豆科药用植物 P.grandiflorum 更相容。除了促进植物生长的性状外，在研究促进植物生长的根际细菌时，还需要考虑植物成分水解活动等特征，并阐明它们的作用。这些菌株对植物生长有益或有害，这可以通过它们对幼苗长度和成熟植物生物量的影响来证明。在本研究中测试的 4 种内生根瘤菌中，潜在的新型根瘤菌属。BF-E16 与非豆科药用植物 P.grandiflorum 更相容。除了促进植物生长的性状外，在研究促进植物生长的根际细菌时，还需要考虑植物成分水解活动等特征，并阐明它们的作用。鉴定出与非豆科药用植物 P.grandiflorum 更相容。除了促进植物生长的性状外，在研究促进植物生长的根际细菌时，还需要考虑植物成分水解活动等特征，并阐明它们的作用。鉴定出与非豆科药用植物 P.grandiflorum 更相容。除了促进植物生长的性状外，在研究促进植物生长的根际细菌时，还需要考虑植物成分水解活动等特征，并阐明它们的作用。