Defensive alteration of root exudate composition by grafting Prunus sp. onto resistant rootstock contributes to reducing crown gall disease

Abstract

Grafting is a traditional and significant strategy to suppress soil-borne 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 roles in suppressing crown gall disease in grafted plants remain 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 were identified. Based on quantitative measurement of the concentrations 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 whereby grafted plants suppress soil-borne disease.

Acknowledgements

The authors thank Lanying Liu and Jing Xu at the Laboratory of Plant Tissue Culture Technology of Haidian District for providing ‘Haiying 1’ seedlings. We thank Dr Dongwei Chen and Prof. Wenbin Du (Chinese Academy of Sciences) for help in the chemotaxis assay. This work was supported by the National Natural Science Foundation of China (grants 32370135 and 31700548) and the Innovation Program of Chinese Academy of Agricultural Sciences (CAAS-CSAL-202302).

Author contributions

Y.L. and L.C. conceived the ideas and designed the methodology; L.B., Y.L., and Q.M. collected the data; L.C. and X.W. analyzed data; L.C. and Y.L. led the writing of the manuscript. All authors contributed critically to the drafts and gave final approval for publication.

Data availability

The 16S rRNA sequence of the tumorigenic strain in sampling area was deposited in GenBank under the accession number OR056166. The Novaseq paired-end reads for the bacterial 16S rRNA gene V3-V4 region from the rhizosphere soil of grafted seedlings and the soil treated with root exudates have been deposited in the NCBI Sequence Read Archive (SRA) database under the accession numbers PRJNA1073026 and PRJNA896915, respectively.

Conflict of interest

The authors declare that they have no conflict of interest.

Supplementary data

Supplementary data are available at Horticulture Research online.

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