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 functions of the microbiome. 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.

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References

Authors

Lin Chen, Lusen Bian, Qinghua Ma, Ying Li, Xinghong Wang,and Yunpeng Liu

Affiliations

1. National Permanent Scientific Research Base for Warm Temperate Zone Forestry of Jiulong Mountain, Experimental Center of Forestry in North China, Chinese Academy of Forestry, Beijing 102300, China

2. State Key Laboratory of Efficient Utilization of Arid and Semi-arid Arable Land in Northern China, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China

About Yunpeng Liu

Prof. Yunpeng Liu focuses on topic of beneficial rhizobacteria, in particular, their interaction with plant. In the past decade, they studied the plant-beneficial functions of Bacillus velezensis, a model strain of beneficial rhizobacteria, and revealed the mechanism underlying the rhizosphere colonization. The findings have been published in journals such as Nature Microbiology, Nature Communications, FEMS Microbiology Reviews, Microbiome, New Phytologist, Horticulture Research, etc.