Tobacco bacterial wilt suppression with biochar soil addition associates to improved soil physiochemical properties and increased rhizosphere bacteria abundance

- Three ton ha−1 biochar amendment reduced tobacco bacterial wilt by >70%.
- Soil physiochemical properties improved in rhizosphere soil after biochar treatment.
- Bacteroidetes increased, while Acidobacteria decreased.
- Ralstonia abundance, which causes tobacco bacterial wilt, was reduced by 94.51%.
- Thus, biochar addition helps protect plants against tobacco bacterial wilt.

This study evaluated the potential use of biochar made from rice straw to control tobacco bacterial wilt (caused by Ralstonia solanacearum) under field conditions. The results showed that 3 ton ha−1 biochar amendment led to a 76.64% reduction in the incidence of the disease a 73.87% drop in the severity of the disease. To elucidate the mechanism by which biochar suppresses the disease, changes to soil physiochemical properties and the microbial community in the tobacco rhizosphere following biochar application were investigated. Compared to the control, physiochemical analysis indicated that rhizosphere soil treated with biochar had higher porosity, pH, cation exchange capacity, organic carbon, alkalized N, available P, and available K, as well as lower bulk density. The V3-V4 section of 16S rRNA and the ITS1 section of the 18S rRNA gene were used to characterize the structure and abundance of the bacterial and fungal communities with the aid of the Illumina Hi Seq system. Biochar addition increased the richness and diversity of the bacterial community in the tobacco rhizosphere. At the phylum level, the abundance of Bacteroidetes was enhanced, while that of Acidobacteria was decreased. In contrast, a smaller increase in fungal gene abundance was detected, with no significant difference in the composition of the fungal community being found between the biochar treatment and the control. The addition of biochar also enriched certain genera of microorganisms, including Steroidobacter, Sphingobium, Caulobacter, Sphingomonas, Sphaerodes, and Mortierella. In contrast, biochar caused the abundance of 10 genera to decline, including Shewanella, Koribacter, Solibacter, Burkholderia, Ralstonia, Neodartorya, Cladirrgunym, Lecythophora, Myrothecium, and Staphylotrichum. In particular, the abundance of Ralstonia, which is the pathogen causing tobacco bacterial wilt, was reduced by 94.51%. Our data suggest that improved soil physiochemical properties and increased bacterial richness and diversity contribute to the ability of biochar to protect plants against tobacco bacterial wilt.