Grafting is a traditional and significant strategy to suppress soilborne diseases, such as the crown gall disease caused by tumorigenic Agrobacterium and Rhizobium. Root exudates and the rhizosphere microbiome play critical roles in controlling crown gall disease, but their role in suppressing crown gall disease by grafted plants remains unclear. Here, disease-susceptible cherry rootstock “Gisela 6” and disease-resistant cherry rootstock “Haiying 1” were grafted onto each other or self-grafted. The effect of their root exudates on the soil microbiome composition and the abundance of pathogenic Agrobacterium were studied. Grafting onto the disease-resistant rootstock helped to reduce the abundance of pathogenic Agrobacterium, accompanied by altering root exudation, enriching potential beneficial bacteria, and changing soil function. Then, the composition of the root exudates from grafted plants was analyzed and the potential compounds responsible for decreasing pathogenic Agrobacterium abundance was identified. Based on quantitative measurement of the concentration of the compounds and testing the impacts of supplied pure chemicals on abundance and chemotaxis of pathogenic Agrobacterium and potential beneficial bacteria, the decreased valine in root exudates of the plant grafted onto resistant rootstock was found to contribute to decreasing Agrobacterium abundance, enriching some potential beneficial bacteria and suppressing crown gall disease. This study provides insights into the mechanism how the grafted plants suppress soil-borne disease.

中文翻译：

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通过嫁接李属植物来防御性改变根系分泌物成分。种植在抗性砧木上有助于减少冠瘿病

嫁接是抑制土传病害的传统且重要的策略，例如由致瘤农杆菌和根瘤菌引起的冠瘿病。根系分泌物和根际微生物组在控制冠瘿病中发挥着关键作用，但它们在嫁接植物抑制冠瘿病中的作用仍不清楚。在此，将易病樱桃砧木“吉塞拉6号”和抗病樱桃砧木“海鹰1号”进行嫁接或自嫁接。研究了其根系分泌物对土壤微生物组组成和致病农杆菌丰度的影响。嫁接到抗病砧木上有助于减少致病性农杆菌的丰度，同时改变根系分泌物，丰富潜在的有益细菌，并改变土壤功能。然后，分析了嫁接植物根系分泌物的成分，并鉴定了导致致病性农杆菌丰度降低的潜在化合物。基于化合物浓度的定量测量并测试所提供的纯化学品对致病性农杆菌和潜在有益细菌的丰度和趋化性的影响，发现嫁接到抗性砧木上的植物根系分泌物中缬氨酸的减少有助于减少农杆菌丰度，富集一些潜在的有益细菌并抑制冠瘿病。这项研究为嫁接植物抑制土传疾病的机制提供了见解。