Autor:innen:
Simon Lewin | Leibniz Centre for Agricultural Landscape Research e.V. (ZALF) | Germany
Prof. Dr. Steffen Kolb | Leibniz Centre for Agricultural Landscape Research e.V. (ZALF) | Germany
Prof. Dr. Sommer Michael | Leibniz Centre for Agricultural Landscape Research e.V. (ZALF) | Germany
Gernot Verch | Leibniz Centre for Agricultural Landscape Research e.V. (ZALF) | Germany
Marc Wehrhan | Leibniz Centre for Agricultural Landscape Research e.V. (ZALF) | Germany
Sonja Wende | Leibniz Centre for Agricultural Landscape Research e.V. (ZALF) | Germany
Paola Ganugi | Università Cattolica del Sacro Cuore | Italy
The rhizosphere microbiome facilitates synergism and competition for plant available nitrogen (N) that is crucial to plant nutrition. Sustainable innovation of agriculture demands reduction of synthetic N fertilizer applications. Thereby, the plant microbiome is envisioned to improve crop N supply. We hypothesized that annual cereal species acquire distinct rhizosphere N cycling guilds regarding its functional and taxonomic composition. Secondly, we assumed, that the dissimilatory nitrate reduction to ammonium (DNRA) and N2 fixation guild will be enriched in slower growing crops, since they may prolong mineral N availability to the plant.
We examined dissimilatory microbial guilds and functions facilitating nitrification, denitrification, DNRA, and N2 fixation within the rhizosphere of winter wheat, rye, and barley. We conducted a field experiment with cereals grown on not or conventionally fertilized plots (n=10; NE Germany, Dedelow) The rhizosphere was sampled during the growth stages tillering and flowering at which plants rely most on soil nutrient uptake. The N-cycling guilds were examined by qPCR based on functional gene markers as well as metagenomics analyses at flowering. These microbial data were correlated to remote sensing of plant aboveground biomass (DRM) as well as soil mineral N content.
Finally, we demonstrated based on regression analyses, that the variation in DRM and grain yield as wells as soil mineral N content explained the abundance of host enriched metabolic N-cycling pathways. Further, we observed divergence of N cycling guilds of the three crop species by metabolic pathway abundances and their functional and taxonomic structure. The DNRA guild was specifically constituted by the nap/nir or nap/nrf pathways within the rhizosphere of rye or wheat, respectively. Additionally, an association of the N2 fixation guild within rye`s rhizosphere persisted. Moreover, canonical bacterial (N fertilized rye) and canonical archaeal (barley, wheat) and complete ammonia oxidizing Bacteria (wheat) were enriched by the crop species, respectively
In conclusion, functional and taxonomic structure of N cycling guilds within the rhizosphere were largely host-specific. Further we provide initial evidence, that this selection process is coupled to crop growth. Hence, we suggest the crop species interaction with N cycling guilds as a crop trait to be evaluated in future research utilizing microbes in agricultural practices.