Molecular Soil Biology 2025, Vol.16, No.5, 241-254 http://bioscipublisher.com/index.php/msb 244 5 Biological Interactions in the Rhizosphere 5.1 Symbiotic associations (mycorrhizae, rhizobacteria) enhancing nutrient acquisition Arbuscular mycorrhizal fungi (AMF) and rhizosphere growth-promoting bacteria (PGPR) are the most important symbiotic microorganisms in the rhizosphere of corn. After symbiosis with roots, AMF can significantly enhance the absorption of insoluble nutrients such as phosphorus and potassium. It can also cooperate with rhizosphere bacteria to further improve the utilization efficiency of insoluble nutrients (Lu et al., 2023). PGPR, such as Bacillus subtilis, can promote root growth and enhance the utilization of water and nutrients. If combined with AMF, it can also enhance drought resistance and yield (Khan et al., 2024). Combined inoculation of multiple microorganisms (such as AMF, Azospirillum, Pseudomonas, Trichoderma) can not only help better colonization of root systems, but also increase the diversity of rhizosphere microorganisms and enzyme activities, and improve soil ecological functions (Xu et al., 2024). 5.2 Root–microbe signaling and soil enzyme activities Corn roots communicate signals with microorganisms through secretions (such as organic acids, flavonoids, etc.), which affects the structure and function of the microbial community. These secretions can attract specific beneficial bacterial communities, such as Oxalobacteraceae, thereby helping to enhance nitrogen absorption and plant growth (Yu et al., 2021). Rhizosphere microorganisms produce a variety of hydrolases (such as β -glucosidase, acid phosphatase, chitinase, etc.), which can accelerate the decomposition of organic matter and the nutrient cycle. The activities of these enzymes are simultaneously regulated by root secretions and microbial community composition (Bilyera et al., 2021; Hao et al., 2022; Yim et al., 2022). If AMF and rhizosphere bacteria act synergistically, they can significantly increase soil enzyme activity and carbon mineralization rate, and optimize rhizosphere nutrient dynamics (Zhou et al., 2022). 5.3 Pathogenic interactions (soil-borne diseases and root defense mechanisms) The rhizosphere microbial community not only promotes nutrient absorption but also acts as a "biological barrier" to prevent the invasion of soil-borne pathogenic bacteria. Corn roots secrete some metabolites (such as benzooxazoline, flavonoids, etc.) to recruit beneficial microorganisms, induce systemic resistance, and thereby enhance the defense ability against pathogenic bacteria (Li et al., 2021). The colonization of AMF on roots can enhance the inhibition of pathogenic fungi (such as Fusarium, Aspergillus, etc.) by the root system, and also increase the activity of rhizoidal enzymes and reduce the occurrence of diseases (Afridi et al., 2022; Ma et al., 2022). The diversity and functionality of the rhizosphere microbial community are important foundations for the health and stress resistance of corn. More sustainable disease management can be achieved by rationally regulating the microbiome (Li et al., 2021; Chepsergon and Moleleki, 2023) (Figure 1). 6 Environmental Stress and Root–Soil Responses 6.1 Drought stress and adaptive root traits Drought is the main abiotic factor that limits corn yield, and it makes the root system show strong plasticity. Under water-deficient conditions, corn can enhance its absorption capacity for deep water by deepening the main root, increasing the distribution of lateral roots, and improving the biomass and surface area of the root system (Guo et al., 2020; Hazman and Kabil, 2021). Meanwhile, the root system increases lignin synthesis, activates hormone signals (such as abscisic acid, brassinolide) and antioxidant defense systems, all of which contribute to improving drought resistance (Jiao et al., 2022; Li et al., 2023; Wang et al., 2025). The presence of root hairs and the increase of secretions can also improve the microbial diversity and enzyme activity in the rhizosphere, thereby helping to retain water and promote nutrient cycling (Gholizadeh et al., 2024; Swift et al., 2024; Yuan et al., 2024; Hartwig et al., 2025). In addition, the combined inoculation of arbuscular mycorrhizal fungi and pro-growth bacteria can significantly improve the hydraulic conductivity, photosynthetic efficiency and hormone regulation of roots, and enhance the tolerance of corn to drought and high temperature (Romero-Munar et al., 2023; Lopes et al., 2025).
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