Summary
Healthy soils that contain an active microbiome and food web are critical to sustainably produce food for a growing global human population. Many studies have focussed on the role of microbial species diversity and the presence of key functional groups as important controls on the many functions that a sustainable food system relies on.
Here, we synthesise recent ecological empirical evidence and theory to propose that the interactions between organisms in the soil food web are the critical determinant of soil function.
We propose the Rhizosphere Interactions for Sustainable Agriculture Model, in which crop roots recruit small, modular, highly connected soil rhizosphere networks from large, static, relatively unconnected and diverse bulk soil networks. We argue that conventional agricultural management disrupts the connections between rhizosphere and bulk soil networks.
Synthesis. We identify future research directions for optimising ecological connections between roots and rhizosphere microbial and faunal networks, and between rhizosphere networks and bulk soil networks in agricultural production systems. Knowledge on these connections can be applied in agricultural systems to sustainability produce food for a growing global population.

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Below-ground connections underlying above-ground food production: a framework for optimising ecological connections in the rhizosphere

Root exudates play an important role in ecosystem response to climate change, but the functional consequences of drought‐induced changes in the quality of root exudates are unknown. Here, we addressed this knowledge gap in a unique experimental approach. We subjected two common grassland species that differ widely in their growth strategies and root systems, the grass Holcus lanatus and the forb Rumex acetosa, to 2 wk of drought. We collected root exudates and soils at the end of the drought and after 2 wk of recovery and readded all root exudates to all soils in a fully reciprocal set‐up to measure root‐exudate‐induced respiration. We found that soil treatment was unimportant for determining root‐exudate‐induced respiration. By contrast, root exudates collected from plants that had experienced drought clearly triggered more soil respiration than exudates from undroughted plants. Importantly, this increased respiration compensated for the lower rates of root exudation in droughted plants. Our findings reveal a novel mechanism through which drought can continue to affect ecosystem carbon cycling, and a potential plant strategy to facilitate regrowth through stimulating microbial activity. These findings have important implications for understanding plant and ecosystem response to drought.

https://nph.onlinelibrary.wiley.com/doi/epdf/10.1111/nph.16001

Changes in root-exudate-induced respiration reveal a novel mechanism through which drought affects ecosystem carbon cycling.

Root functional traits explain root exudation rate and composition across a range of grassland species

Soil potentials to resist continuous cropping obstacle: three field cases

The secretion of allelochemicals from plant roots plays a key role in soil sickness and soil-borne disease. The goal of this study was to investigate the role of allelopathic chemicals in Ralstonia solanacearum-infected tobacco roots. The organic acids investigated in the present study are major components of tobacco root exudates. Through a swarming assay, we assessed the chemotaxis and colonization of R. solanacearum in response to organic acids. Fumaric acid was detected, and the results showed that this acid could serve as a semiochemical for attracting R. solanacearum and inducing the formation of biofilms of this species. The results also revealed that cinnamic and myristic acids play significant roles on swarming motility and chemotaxis. In addition, cinnamic, myristic and fumaric acids could enhance the expression of chemotaxis- and motility-related genes in R. solanacearum cultured in minimal medium. Furthermore, these three acids promote R. solanacearum colonization and accelerate disease progression in tobacco. Cinnamic, myristic and fumaric acids could serve as semiochemical attractants to induce the colonization and infection of R. solanacearum. The results of the present study enhance our understanding of the ecological effects of plant root exudates in plant-microbe interactions and help to reveal the relationship between tobacco bacterial wilt and the autotoxins and allelochemicals that accumulate from root exudates.

Cinnamic, myristic and fumaric acids in tobacco root exudates induce the infection of plants by Ralstonia solanacearum

Identification of benzoic acid and 3-phenylpropanoic acid in tobacco root exudates and their role in the growth of rhizosphere microorganisms

The invention discloses a screening method of a pseudomonas solanacearum bacteriophage resource. The screening method comprises the following steps: S1, taking a soil sample, treating the sample, and filtering by a filter membrane to obtain a filtrate; S2, culturing a pseudomonas solanacearum strain to obtain a pseudomonas solanacearum liquid; S3, co-culturing the filtrate in the S1 and the pseudomonas solanacearum in the S2; and S4, selecting and storing bacteriophage plaque, wherein the used material comprises sterile water, the pseudomonas solanacearum strain, a CPG culture medium, agar powder and low-melting-point agar. The CPG culture medium comprises a CPG solid culture medium and a CPG liquid culture medium. The method can be applied to screening the pseudomonas solanacearum bacteriophage resource from tobacco-planting soil, bacterial wilt soil and sewage and providing and collecting the pseudomonas solanacearum bacteriophage resource for researching prevention and control of tobacco bacterial wilt by using the pseudomonas solanacearum bacteriophage.

Screening method of pseudomonas solanacearum bacteriophage resource

The present invention discloses a special tobacco trace element slow-release additive, a production method and a use method. Raw materials of the special tobacco trace element slow-release additive comprise, by mass, 0.25-0.35 part of trace elements, 8-12 parts of water, and 0.4-0.6 part of a water retaining agent. According to the present invention, the water retaining agent is adopted to absorb the trace elements, and a protection agent and an organic fertilizer are mixed during use, such that the trace elements in the water retaining agent are gradually released when tobacco roots absorb the fertilizer, and are effectively absorbed by the tobacco roots so as to avoid curing due to combination of the trace elements and other ions in the soil, substantially increase utilization rate of the trace elements, and concurrently meet bioavailability and chemical effectiveness; and the conventional thinking of the technical staff in the field is broken, development is performed towards the professional targeting from the multieffect pursuit, and the trace element slow-release additive can be mixed with different organic fertilizers so as to increase yields.

Lu Ning

Papers

Identification of benzoic acid and 3-phenylpropanoic acid in tobacco root exudates and their role in the growth of rhizosphere microorganisms

Screening method of pseudomonas solanacearum bacteriophage resource

Special tobacco trace element slow-release additive, production method and use method