Nanotechnology and Plant-Microbe Interactions: Enhancing Symbiotic Relationships for Crop Resilience

The integration of nanomaterials (NMs) with plant-beneficial microorganisms has emerged as a promising strategy to improve crop resilience to abiotic stresses. Evidence from multiple studies indicates that NM-microbe co-application often enhances plant growth, nutrient uptake, biomass accumulation, and stress tolerance more effectively than either approach alone. Under drought and salinity stress, these combinations help maintain ionic balance, particularly higher K+/Na+ ratios, sustain photosynthesis, and reduce oxidative damage by increasing the activities of antioxidant enzymes such as superoxide dismutase, catalase, and peroxidase. Nanoparticles, including ZnO, Fe3O4, and SiO2, when combined with plant growth-promoting rhizobacteria (PGPR) or arbuscular mycorrhizal fungi (AMF), stimulate root development, increasing water and nutrient acquisition. Additionally, NMs can reshape rhizosphere microbial communities by enriching beneficial taxa such as Pseudomonas, Bacillus, and Trichoderma while suppressing certain phytopathogens. Nanoformulated fertilizers and micronutrients further enhance nutrient use efficiency and may reduce dependence on conventional agrochemicals, supporting sustainable agricultural practices. However, the benefits of NM-microbe integration are not universal. Several studies report that some nanomaterials can inhibit beneficial microorganisms, including nitrogen-fixing bacteria and AMF, at concentrations only slightly above stimulatory levels, highlighting a narrow safety margin. Concerns also remain regarding NM persistence, soil-dependent mobility, trophic transfer through food webs, and potential disruption of soil microbial communities. This review evaluates both the advantages and risks of NM-microbe interactions, emphasizing the importance of dose, soil characteristics, and microbial strain selection. Current evidence, largely derived from short-term laboratory studies, remains insufficient to support widespread field application without long-term ecological monitoring, standardized assessment protocols, and evaluation of economic feasibility for smallholder farming systems.