Simulated soil erosion predominantly affects fungal abundance in the rapeseed rhizosphere

• Published in: Rhizosphere Vol. 30; p. 100912
• Main Authors: Ruggaber, Julian, Pehlivan, Ayten, Remus, Rainer, Francioli, Davide, Wirth, Stephan, Augustin, Jürgen, Kolb, Steffen
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.06.2024
• Subjects: 14C pulse labeling; Fungi qPCR; ITS metabarcoding; Microbial biomass; 14C pulse labeling; ITS metabarcoding; Microbial biomass; Fungi qPCR
• ISSN: 2452-2198; 2452-2198
• DOI: 10.1016/j.rhisph.2024.100912

Eroded agricultural soils have reduced soil organic carbon (SOC) levels that may affect the plant-microbiome interactions in the rhizosphere. We explored the impact of simulated erosion on major microbial groups in a pot experiment with rapeseed (Brassica napus L.) grown on arable soil with the potential to capture SOC. An erosion gradient was simulated by admixture (0%, 12%, 24%) of subsoil horizon (Bt) to topsoil (Ap) material. Rapeseed plants were pulse-labeled with 14CO2 at three growth stages and two soil compartments (bulk and rhizosphere soil) were sampled. Fungal ITS copy numbers were consistently higher in the rhizosphere and decreased with progressing plant growth stages. A significant increase of bacterial 16S rRNA gene copies in the rhizosphere only occurred at flowering. A response of fungal abundance to subsoil admixture was found detectable based on fungi:Bacteria and fungi:Archaea ratio at flowering. Archaea were neither affected by soil compartment nor subsoil admixture. 14C activity of microbial biomass, an indicator for relative input of freshly assimilated C into soil microbiome, was impacted by growth stage and compartment and decreased with ongoing growth stage. During the rosette growth stage, the 14C activity of the microbial biomass was elevated in the rhizosphere of the eroded soil indicating a plant response to the erosion factor. Our experiment revealed a compositional separation of the fungal community along the simulated erosion gradient and a selection of fungi for the two different soil compartments at flowering. Olpidimycetes, Fusarium and Rhizopus and putative pathogens were enriched in the rhizosphere at flowering. Fungi may have a competitive advantage in the rhizosphere of strongly eroded and nutrient diluted soils due to ecological adaptation and morphological traits i.e. hyphae that can bypass soil areas with low nutrient availability.