Shifts Between and Among Populations of Wheat Rhizosphere Pseudomonas, Streptomyces and Phyllobacterium Suggest Consistent Phosphate Mobilization at Different Wheat Growth Stages Under Abiotic Stress

Abstract

Climate change models predict more frequent and prolonged drought events in Central Europe, which will exert extraordinary pressure on agroecosystems. One of the consequences is drought-related nutrient limitations for crops negatively affecting agricultural productivity. These effects can be mitigated by beneficial plant growth promoting rhizobacteria. In this study, we investigated the potential of cultivable bacterial species for phosphate solubilization in the rhizosphere of winter wheat at two relevant growth stages-stem elongation and grain filling stages. Rhizosphere samples were collected in the Global Change Experimental Facility in Central Germany, which comprises plots with conventional and organic farming systems under ambient and future climate. Phosphate-solubilizing bacteria were selectively isolated on Pikovskaya medium, phylogenetically classified by 16S rRNA sequencing, and tested for in vitro mineral phosphate solubilization and drought tolerance using plate assays. The culture isolates were dominated by members of the genera Phyllobacterium, Pseudomonas and Streptomyces. Cultivation-derived species richness and abundance of dominant taxa, especially within the genera Phyllobacterium and Pseudomonas, as well as composition of Pseudomonas species were affected by wheat growth stage. Pseudomonas was found to be more abundant at stem elongation than at grain filling, while for Phyllobacterium the opposite pattern was observed. The abundance of Streptomyces isolates remained stable throughout the studied growth stages. The temporal shifts in the cultivable fraction of the community along with considerable P solubilization potentials of Phyllobacterium and Pseudomonas species suggest functional redundancy between and among genera at different wheat growth stages. Phosphate-solubilizing Phyllobacterium species were assigned to Phyllobacterium

Interactions between soil properties, agricultural management and cultivar type drive structural and functional adaptations of the wheat rhizosphere microbiome to drought

“…Both community structure and its trait composition are steered by various environmental factors. Vegetation cover (Francioli et al, 2018) and plant growth stage (Wang et al, 2016;Breitkreuz et al, 2020), as well as soil moisture dynamics, alter composition and traits of soil and plant rhizosphere communities prominently (De Vries et al, 2012;Santos-Medellín et al, 2017;Ochoa-Hueso et al, 2018). Moreover, Lauber et al (2008) found that the microbial community structure is strongly affected by soil type, a finding that was further supported by a study comparing soil bacteria as well as fungi-dominated food webs across various European field sites (de Vries et al, 2013).…”

Flooding Causes Dramatic Compositional Shifts and Depletion of Putative Beneficial Bacteria on the Spring Wheat Microbiota

“…Using a metabarcoding approach, we monitored responses of the bacterial community associated with different wheat compartments (rhizosphere and root) to flooding stress. Since plant phenology is an important driver in plant microbiota assembly (Donn et al, 2015;Francioli et al, 2018), and abiotic stress might affect differentially the plant-microbiota complex depending on the specific plant growth stage (PGS) in which it occur (Na et al, 2019;Breitkreuz et al, 2020), we imposed flooding stress only once, either at tillering, booting or flowering. Moreover, several soil and plant traits were measured through the whole experiment to correlate edaphic and physiological plant changes with shifts in bacterial community assemblage.…”

Drought and Plant Community Composition Affect the Metabolic and Genotypic Diversity of Pseudomonas Strains in Grassland Soils

“…Recently, we investigated the potential of cultivable bacterial species for phosphate solubilization in the rhizosphere of winter wheat. Wheat stem elongation stage was associated with a high abundance of Pseudomonas , but also at the grain filling stage with Phyllobacterium [ 65 ]. Since the members of the clusters 1 and 2 also responded to PCC, both plant-derived compounds and changes in soil properties and temperature may play out in the differential seasonal distribution of this group.…”