Analysis of microbial communities in rhizosphere soil for flue-cured tobacco varieties (lines) with different resistance to bacterial wilt

To investigate the relationships between rhizosphere microbial community, soil factors and the occurrence of tobacco bacterial wilt and the resistance mechanism of flue-cured tobacco to infection by Ralstonia solanacearum, metagenomics high-throughput sequencing technology was used to study the differences in rhizosphere soil microbial community, rhizosphere soil nutrients and enzyme activities of the highly resistant strain Cuibi No.1 mutant (633K) and the highly susceptible Honghuadajinyuan (HD) under pot conditions. The results showed that the relative abundance of microbial genera such as Sphingomonas and Bradyrhizobium in 633K rhizosphere soil was higher than that in HD rhizosphere soil, while the relative abundance of Rhodanobacter and Castellaniella was higher in HD rhizosphere soil. Compared to HD, the species diversity and structural complexity of the dominant species network in the 633K rhizosphere soil decreased after Ralstonia solanacearum infection. The dominant strains with high correlations in the 633K rhizosphere soil microbial network were mainly beneficial bacteria such as Solirubrobacter pauli, Solirubrobacter soli and Edaphobacter aggregans, while the dominant strains with high correlations in the HD rhizosphere soil microbial network were mainly harmful bacteria such as Dyella jiangningensis. The contents of nitrate nitrogen (NO₃^--N), ammonium nitrogen (NH₄⁺-N), microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) and urease activity (S-UE) in 633K rhizosphere soil were significantly higher than those in HD rhizosphere soil, which were 143.73%, 80.05%, 154.42%, 44.85% and 21.50% higher than those in HD rhizosphere soil, respectively. However, acid phosphatase (S-ACP) and sucrase (S-SC) activities and organic matter (SOM) content in 633K rhizosphere soil were significantly lower than those in HD rhizosphere soil, which decreased by 47.36%, 31.97% and 26.13%, respectively. Redundancy analysis showed that microbial biomass carbon was significantly correlated with microbial community structure and had the highest contribution to microbial community structure.