Abstract: Plant root system architecture is the growth and distribution of the root system in its growth medium, include root length, number, branch and biomass, etc, which can fix plants in the soil and effectively absorb water and mineral nutrients, which directly affect the growth and development of plants. The root system architecture is affected by many factors, including soil moisture, nutrients and rhizosphere microorganisms. Conventional root ameliorated practices often rely on chemical fertilizers, which have immense and adverse effects on environments. Therefore, it is necessary to propose alternatives to chemical fertilizers. The rhizosphere of the plant is an essential niche with abundant microorganisms residing in it, those rhizospheric microbes link the interaction of plants and soil to promote nutrient solubilization and they possess the properties of the primary root, lateral root and root hair growth ameliorated as the second genome of the plant. The application in the techniques of multi-omic analysis (genomics-metabolomics, genomics-transcriptomics, etc) can explore deeply related mechanisms for beneficial microbes affect root development. These mechanisms are of great importance in improving soil fertility and plant growth, thus reducing the negative impact of chemical fertilizers on the environment. Therefore, the aim of this paper was to review the research methods, effects and mechanisms of root system architecture regulated by plant rhizosphere microorganisms. The results indicated that AMF, PGPR and rhizobium increased root length, root diameter, root branch and promoted root hair and lateral root development through four mechanisms (nitrogen fixation, phosphate solubilization, regulation of plant secretion of plant hormones, and release of volatile organic compounds). Above all, plant rhizosphere microorganisms can improve root system architecture, but the effect of plant rhizosphere microorganism’s application still needs to be further studied. Quantifying the relative contributions of different mechanisms and improving the stability of microbial inoculants in practical applications are the focus of follow-up research. These conclusions will provide a theoretical basis for the development of microbial inoculants.

Key words: Root system architecture, Arbuscular mycorrhizal fungi, Rhizobium, Plant growth promoting rhizobacteria, Microbial inoculants