Ralstonia solanacearum biovar2-race3 (Rs r3b2) is an epidemic soil-borne bacterial phytopathogen causing brown rot disease in potato. In this study, we assessed how three soil types stored at the same field site influenced the proportion and diversity of bacterial isolates with in vitro antagonistic activity towards Rs in bulk soil and different potato plant spheres (rhizosphere, endorhiza and endocaulosphere; ecto- and endosphere of seed and yield tubers). In general, the plate counts observed for each sample type were not significantly different. A total of 96 colonies per sample type was picked and screened for in vitro antagonistic activity against Rs. Antagonists were obtained from all bulk soils and plant spheres with the highest proportion obtained from the endorhiza and endocaulosphere of potato plants. BOX-PCR fingerprints of antagonists showed that some were specific for particular plant spheres independent of the soil type, while others originated from different plant spheres of a particular soil type. The majority of antagonists belonged to Pseudomonas. A high proportion of antagonists produced siderophores, and interestingly antagonists from potato tubers frequently carried multiple antibiotic production genes. Our data showed an enrichment of bacteria with genes or traits potentially involved in biocontrol in the rhizosphere and in endophytic compartments. We report that the proportion and diversity of in vitro antagonists towards Rs isolated from bulk soil and different spheres of potato plants grown under field conditions in three different soil types was mainly shaped by the plant sphere and to a lesser extent by the soil type. Bacteria with antagonistic activity towards Ralstonia solanacearum were isolated from all plant spheres and bulk soils but their proportion was highest in endophytic compartments

中文翻译：

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马铃薯植物球体和较小程度的土壤类型影响对青枯菌具有体外拮抗活性的细菌分离物的比例和多样性

Ralstonia solanacearum biovar2-race3 (Rs r3b2) 是一种流行的土壤传播细菌植物病原体，可导致马铃薯褐腐病。在这项研究中，我们评估了储存在同一田地的三种土壤类型如何影响在散装土壤和不同马铃薯植物球体（根际、内生根和内生圈；外生圈和内生圈）中对 Rs 具有体外拮抗活性的细菌分离物的比例和多样性。种子和产量块茎）。一般来说，观察到的每种样品类型的平板计数没有显着差异。每种样品类型总共挑选了 96 个菌落，并筛选了针对 Rs 的体外拮抗活性。拮抗剂是从所有大块土壤和植物球中获得的，其中马铃薯植物的内根和内茎球比例最高。拮抗剂的 BOX-PCR 指纹图谱表明，一些拮抗剂对特定的植物球体具有特异性，与土壤类型无关，而另一些则来自特定土壤类​​型的不同植物球体。大多数拮抗剂属于假单胞菌属。高比例的拮抗剂产生铁载体，有趣的是来自马铃薯块茎的拮抗剂经常携带多种抗生素生产基因。我们的数据显示了细菌的富集，这些细菌具有可能参与根际和内生区生物防治的基因或性状。我们报告说，在三种不同土壤类型的田间条件下生长的马铃薯植物的大块土壤和不同球体中分离出的 Rs 的体外拮抗剂的比例和多样性主要受植物球体的影响，而在较小程度上受土壤类型的影响。