Abstract:

The development and application of microbial inoculants is of high importance to addressing the decline in cultivated land quality in China and implementation of biological remediation technologies. This study investigated the plant growth-promoting traits of Burkholderia sp. strain SX9 and evaluated its effects on white clover （Trifolium repens） growth， rhizosphere soil physicochemical properties， and microbial communities in pot experiments. Treatments included varying concentrations of bacterial inoculants （original solution， 500-fold dilution and 1000-fold dilution； T₁-T₃，_{respectively）， culture solutions （original solution， 500-fold dilution and 1000-fold dilution， T4-T6， respectively）， and purified water （CK）. It was found that Burkholderia sp. strain SX9 exhibited multiple growth-promoting characteristics， including cellulase， protease and ammonia production. Compared with CK and T4， T1 （original inoculant） significantly increased soluble sugar content in white clover by 60.6% and 31.3%， soluble protein content by 43.3% and 15.5%， and root length by 20.3% and 5.48%， respectively. White clover cultivation improved the pH of rhizosphere soil. T1 enhanced electrical conductivity， with available phosphorus and potassium increasing by 27.2% and 9.27% compared to T4. Additionally， T1 and T2 accelerated organic matter decomposition； T1 organic matter content decreased by 5.23% relative to T4， and T2 by 2.07% relative to T5. Alpha diversity analysis revealed that T1 significantly reduced fungal and bacterial richness， diversity， and evenness in rhizosphere soil. High-throughput sequencing indicated that T1 decreased the relative abundance of Ascomycota， Penicillium， and Aspergillus while increasing Humicola and unclassified fungi. For bacteria， T1 reduced Actinobacteriota， Acidobacteriota， Unnamed genus 67-14， and Acidothermus， but elevated Proteobacteria， Burkholderia-Caballeronia-Paraburkholderia， and unclassified bacteria. Correlation analysis revealed that pH positively correlated with Acidobacteriota but negatively with Basidiomycota. Available phosphorus and potassium showed positive associations with Basidiomycota， Actinobacteriota， and Gemmatimonadota， but negative correlations with Ascomycota， Glomeromycota， and Chloroflexi. Organic matter content was negatively correlated with Proteobacteria and Gemmatimonadota. The research results show that Burkholderia sp. SX9 enhances white clover growth， improves soil fertility， and dynamically reshapes rhizosphere microbial communities. These findings provide scientific data to inform further research and underpin development of soil improvement strategies.}

Key words: Burkholderia sp., Trifolium repens, rhizosphere, microbial community