Effect of continuous sorghum cropping on the rhizosphere microbial community and the role of Bacillus amyloliquefaciens in altering the microbial composition

Abstract

This study explored variations in the rhizosphere microbial community composition resulting from the continuous cropping of sorghum. We explored the potential growth-promoting effects of Bacillus amyloliquefaciens in manipulating the microbial community composition of the rhizosphere soil under continuous cropping. Illumina MiSeq sequencing was used to compare the composition of the bacterial and fungal communities in the rhizosphere soil from a sorghum–maize rotation system, sorghum continuous cropping system, and sorghum continuous cropping with the application of the biological agent B. amyloliquefaciens. The rhizosphere soil under continuous sorghum cropping had lower bacterial richness and higher fungal diversity than the sorghum–maize rotation rhizosphere soil. The bacterial phyla Acidobacteria and Gemmatimonadetes, and the fungal phylum Basidiomycota, were strongly enriched in the continuous cropping soil. The class Tremellomycetes was the most dominant group, accounting for 19.30% of the total fungal sequences in the continuous cropping soil and 4.51% in sorghum-maize rotation soil. Application of B. amyloliquefaciens significantly decreased the abundance of Tremellomycetes by 8.87% in the continuous cropping soil. Our results indicate that the decrease in sorghum growth and yield under continuous cropping are in coincidence with the alteration of soil microbial community composition, particularly the accumulation of Tremellomycetes in the continuously cropped rhizosphere soil. Our findings contribute to an improved understanding of the effects of continuous sorghum cropping on soil microbiome, and B. amyloliquefaciens can be used to manipulate the microbial communities of the sorghum rhizosphere soil.