Plant–Microbiome Interactions for Environmental Resilience: Rhizosphere Ecology, Climate Adaptation and Ecosystem Sustainability

Plant–Microbiome Interactions under Climate Extremes: A Critical Review of Rhizosphere Assembly, Stress Adaptation and Environmental Resilience

2026-10-06T12:42:07+00:00

Droughts, heatwaves, floods and salinisation are becoming more frequent and more intense, and their consequences for crops and natural vegetation are increasingly understood to depend on the microorganisms that live on and within roots. Research on the rhizosphere microbiome has expanded rapidly, yet the literature remains fragmented across extreme types, experimental systems and disciplinary traditions, and it frequently conflates compositional change with functional benefit. This critical narrative review examines how climate extremes alter the assembly of root-associated microbial communities, which mechanisms plausibly link these changes to plant stress adaptation, and under what conditions microbial responses contribute to the resilience of plants, soils and ecosystems. Peer-reviewed literature was identified through structured searches of biomedical, life-science and multidisciplinary scholarly indexes, supplemented by backward and forward citation tracking, and was appraised for experimental design, ecological realism, causal inference and replication. The synthesis indicates that drought produces the most consistent and best-replicated signal, namely the enrichment of monoderm bacteria, particularly Actinobacteria, in root compartments across many grass and non-grass hosts, whereas the responses to heat, flooding and compound extremes are less consistently characterised and rest on fewer, often greenhouse-based studies. Mechanistic evidence is strongest for individual microbial functions, such as the degradation of the ethylene precursor 1-aminocyclopropane-1-carboxylate, iron-related processes and mycorrhizal water transport, but evidence that whole communities are actively recruited to protect the host remains largely correlative. Soil microbial legacies of past drought can modify later plant responses, although these benefits are contingent on host species, soil history and the timing of stress. Translational approaches, including inoculants, synthetic communities and host-mediated selection, show consistent benefits in controlled settings but variable establishment and performance in the field. Major unresolved questions concern causality at the community scale, the durability of legacy effects, the realism of imposed extremes, the geographical concentration of evidence and the scarcity of multi-season field trials. A predictive understanding of microbially mediated resilience will require experiments that combine realistic extreme regimes, quantitative microbial measurements and host-phenotype outcomes across contrasting soils and climates.

Engineering the Rhizosphere Microbiome for Climate-Resilient Agriculture: A Critical Appraisal of Synthetic Communities, Host Genetic Control and Precision Microbial Design

2026-10-06T12:52:42+00:00

Rising temperatures, more erratic rainfall and expanding soil salinisation are eroding the stability of cropping systems, and the microbial communities inhabiting the rhizosphere have been proposed as a tractable lever for restoring that stability. Three research programmes now dominate this ambition: the assembly of defined synthetic communities from culturable isolates, the exploitation of host genetic variation that shapes microbial recruitment, and the computational or synthetic-biology design of microbial functions targeted at specific agronomic outcomes. These programmes have developed largely in parallel, are evaluated against different standards of proof, and are frequently presented in a common narrative of imminent application that the underlying evidence does not yet support. This review critically examines the strength, consistency and translational maturity of the evidence in each programme and interrogates the assumptions that connect them. Peer-reviewed literature published between January 2012 and 27 July 2026 was identified through structured searching of biomedical, agricultural and multidisciplinary scholarly indexes, complemented by backward and forward citation tracking and verification of bibliographic identity through a digital object identifier registry. Evidence was appraised for design adequacy, environmental realism, replication and the distance between mechanistic demonstration and field performance. The synthesis indicates that host genetic effects on rhizosphere community composition are statistically detectable but generally modest relative to soil and environmental effects, that single-locus exemplars have been disproportionately influential in shaping expectations, and that synthetic communities reliably establish causality under controlled conditions while rarely demonstrating durable colonisation or yield benefit in the field. Reported successes cluster in a small number of model species, glasshouse systems and short observation windows, and negative or equivocal results appear underrepresented. Confidence is highest for mechanistic claims about exudate-mediated recruitment and lowest for claims about transferable, climate-buffering performance at agronomic scale. Progress will depend less on additional descriptive surveys than on multi-environment trials, quantitative measurement of strain persistence, pre-registered field evaluation and explicit treatment of ecological containment.

Root Exudates as Ecological Signals: A Critical Review of Metabolic Control over Rhizosphere Microbiome Assembly and Plant Adaptation

2026-10-06T12:57:11+00:00

Plant roots release a chemically diverse mixture of primary and specialised metabolites into the surrounding soil, and this exudation is now widely invoked as the principal means by which plants select, structure and exploit their rhizosphere microbiota. The proposition that exudates function as ecological signals, rather than as nutrient leakage that microorganisms passively consume, carries substantial theoretical and applied weight, yet the evidence for it is uneven. This critical narrative review evaluates what is known about the metabolic control of rhizosphere microbiome assembly and its consequences for plant adaptation to biotic and abiotic stress. Literature published between January 2000 and 27 July 2026 was identified through structured searches of multidisciplinary and life-science bibliographic sources, supplemented by citation tracking, and was appraised for design, causal inference, ecological realism and consistency. The synthesis distinguishes four explanatory layers: a broad substrate-driven filter imposed by sugars, organic acids and amino acids; selective gatekeeping by specialised metabolites such as coumarins, benzoxazinoids, triterpenes, flavonoids and saponins; reciprocal modulation of exudation by the microbiota itself; and stress-responsive shifts in exudation that recruit microorganisms associated with improved host performance. Genetic evidence from biosynthetic and transporter mutants now establishes that individual metabolite classes can reshape community composition, and several studies link these shifts to host iron nutrition, nitrogen acquisition, pathogen suppression or drought recovery. Confidence remains limited by the predominance of gnotobiotic and hydroponic systems, the difficulty of sampling exudates in soil without artefact, the small spatial reach of many compounds, strong effects of soil type that frequently outweigh host chemistry, and scarce field validation. The term signal is often applied without evidence that the response is adaptive for both partners. The review argues that exudate-mediated assembly is best treated as conditional niche construction whose outcomes depend on soil context, microbial tolerance traits and developmental timing. Priorities include spatially resolved exudate measurement in soil, multi-site field trials with defined genetic variants, and explicit tests of fitness consequences across plant generations.

Plant–Soil–Microbiome Feedbacks in a Changing Climate: A Critical Synthesis of Links among Biodiversity, Biogeochemical Cycling and Ecosystem Multifunctionality

2026-10-06T13:01:16+00:00

Plants modify the biotic and abiotic properties of the soil in which they grow, and these modifications subsequently alter the performance of the same or other plant species. Such plant–soil feedbacks, which operate largely through the soil microbiome, have become central to explanations of plant coexistence, invasion, succession and the persistence of soil carbon. Climate change now alters every component of this loop simultaneously, yet the literature remains fragmented among community ecology, microbial ecology and biogeochemistry, and existing reviews rarely evaluate whether evidence from these fields can be combined to predict the functioning of whole ecosystems. This critical narrative review examines how drought, altered precipitation, warming, elevated atmospheric carbon dioxide and nitrogen enrichment reshape plant–soil–microbiome feedbacks, and how those changes propagate to plant diversity, carbon and nitrogen cycling, and ecosystem multifunctionality. Literature was identified through structured searches of multidisciplinary scholarly indexes, supplemented by citation tracking, and was appraised for design, scale, duration and consistency with independent evidence. The synthesis indicates that drought frequently shifts feedbacks, although the direction of change depends on plant functional group, mycorrhizal association, drought history and whether experiments are conducted in the field or under controlled conditions. Evidence for warming effects on feedbacks is weaker and less consistent than evidence for warming effects on microbial respiration and diversity. Mycorrhizal type emerges as the most transferable organising axis, linking feedback direction, nutrient economies and carbon storage. Positive associations between soil biodiversity and multifunctionality are well documented in observational surveys, but their causal basis, their stability under multiple simultaneous stressors and their dependence on aridity remain unresolved. The dominant constraints are short experimental duration, reliance on glasshouse bioassays, inconsistent feedback metrics and a geographical concentration of studies in temperate grasslands. Priorities include long-term field experiments with factorial climate treatments, reciprocal inoculation along climatic gradients, standardised feedback and multifunctionality metrics, and process-based models that represent microbial physiology explicitly. Current evidence supports treating plant–soil–microbiome feedbacks as a conditional, rather than universal, regulator of ecosystem responses to climate change.

Microbiome-Mediated Plant Tolerance to Drought, Heat, Salinity and Flooding: A Critical Review of Mechanisms, Trade-Offs and Translational Opportunities

2026-10-06T13:05:37+00:00

Drought, extreme heat, soil salinity and flooding are the abiotic stresses most likely to intensify under climate change, and each already constrains crop yield across large agricultural regions. Plant-associated microorganisms, including rhizosphere and endophytic bacteria, arbuscular mycorrhizal fungi and other fungal endophytes, can modify how plants experience and recover from these stresses. Interest in harnessing such microorganisms has expanded rapidly, yet the literature remains fragmented by stressor, by microbial group and by experimental scale, and many published claims rest on single-strain, single-host experiments under controlled conditions. This critical narrative review evaluates evidence published from 2000 onwards, together with foundational earlier work, identified through structured searches of multidisciplinary and life-science indexes, citation tracking and examination of recent reviews and meta-analyses. The synthesis is organised around four questions: which mechanisms are supported for each stressor, how consistently they operate across hosts and environments, what costs and conflicts accompany microbial benefits, and which translational routes are credible. The evidence is strongest for ethylene modulation through bacterial 1-aminocyclopropane-1-carboxylate deaminase, for mycorrhizal effects on plant water relations and sodium exclusion, and for drought-driven restructuring of root microbiomes that enriches monoderm bacteria such as Streptomyces. Evidence for heat tolerance is mechanistically striking but taxonomically narrow, and evidence for flooding tolerance is the least developed, with anaerobic shifts frequently depleting putatively beneficial taxa. Benefits are strongly context dependent: they vary with host genotype, soil history, stress intensity and combinations of stresses, and mycorrhizal carbon costs, growth–defence interactions and opposing hormonal requirements across stressors can reverse apparent advantages. Greenhouse findings predict field outcomes poorly, and in vitro screening for growth-promoting traits has limited predictive value. Synthetic communities, host-mediated selection, breeding for microbiome recruitment and the use of microbial legacies represent promising but largely unvalidated routes. Progress now depends on multi-site field trials with standardised tolerance metrics, mechanistic validation with microbial and plant mutants, explicit accounting of costs, and studies of combined and sequential stresses. Microbiome-mediated tolerance is best regarded as a conditional, manageable component of crop resilience rather than a generic substitute for breeding or agronomic adaptation.

Plant–Microbiome Partnerships in the Restoration of Degraded Terrestrial Ecosystems: A Critical Review of Soil Microbiome Recovery, Ecological Resilience and Nature-Based Solutions

2026-10-06T13:08:51+00:00

Land degradation disrupts the partnerships between plants and soil micro-organisms that sustain nutrient cycling, soil structure, carbon storage and plant community assembly. Restoration practice has historically concentrated on vegetation and abiotic conditions, whereas the soil microbiome has usually been treated as a passive indicator that is expected to recover once plants return. This critical narrative review evaluates whether that expectation is justified and examines when deliberate manipulation of plant–microbiome partnerships improves restoration outcomes. Peer-reviewed literature published from January 2000 to 27 July 2026 was identified through multidisciplinary scholarly indexes, citation tracking and institutional sources, and was appraised for design, scale, duration and consistency with independent evidence. Five themes emerged. First, global syntheses and chronosequences show that revegetation moves soil microbial composition towards reference conditions, but a persistent restoration gap remains; bacteria generally recover faster than fungi, and microbial richness is a poor marker of recovery. Second, active interventions such as whole-soil transfer and native mycorrhizal inoculation can steer plant community trajectories and favour late-successional species, but effects depend strongly on inoculum origin, dose, site preparation and plant functional type. Third, commercial inoculants frequently show low viability and weak field performance, and deliberate introductions can reorganise resident communities in ways that are rarely monitored for long enough to judge persistence or harm. Fourth, evidence that restored microbiomes confer ecological resilience rests mainly on correlative network analyses and short-term drought experiments, so causal links between microbial recovery and ecosystem stability remain insufficiently tested. Fifth, the inclusion of soil microbiomes in nature-based solutions is conceptually well founded through carbon stabilisation, soil aggregation and possible human-health co-benefits, but standardised microbial indicators, reference states and governance of inoculant use are underdeveloped. The review concludes that plant–microbiome partnerships are a necessary but conditional component of ecological restoration. Their value is best supported where degradation has depleted microbial propagules and where locally sourced inocula are matched to site conditions. Long-term, replicated field experiments with functional and multi-kingdom monitoring are required before microbial restoration can be prescribed with confidence at landscape scales.

Rhizosphere Ecology and Plant–Microbe Symbioses: A Critical Narrative Review from Fundamental Interactions to Sustainable and Climate-Resilient Ecosystems

2026-10-06T13:13:36+00:00

The rhizosphere, the narrow and dynamic zone of soil shaped by living roots, hosts some of the most consequential biological interactions on Earth. Root-associated microorganisms and symbionts influence plant nutrition, immunity, stress tolerance, soil carbon formation and ecosystem stability, and they are increasingly proposed as tools for reducing fertiliser and pesticide dependence and for adapting agriculture to climate change. Enthusiasm for microbiome-based solutions has nevertheless outpaced the evidence in several areas, and the literature combines rigorous mechanistic work with correlative surveys, optimistic extrapolation and inconsistent field outcomes. This critical narrative review evaluates what is known, what is contested and what remains speculative across the continuum from fundamental rhizosphere processes to applied and climate-oriented management. Peer-reviewed literature was identified through structured searching of multidisciplinary and biomedical bibliographic sources, supplemented by citation tracking, with emphasis on evidence published from 2005 onwards and inclusion of earlier foundational work. The synthesis examines five linked themes: the spatial and chemical definition of the rhizosphere; the assembly of root-associated microbiomes under soil, host and microbial control; the mechanisms, costs and context dependency of arbuscular mycorrhizal, rhizobial and associative symbioses; rhizosphere contributions to plant health, nutrient supply and soil carbon; and the responses of root–microbe systems to drought, warming and elevated carbon dioxide. Evidence is strongest for soil as the principal source of root microbiota, for host filtering of community composition, for the molecular basis of the major mutualisms and for context-dependent benefits of symbiosis. Evidence is weaker and frequently overstated for the general efficacy of commercial inoculants, the functional importance of common mycorrhizal networks in forests, the transferability of laboratory-defined synthetic communities to farms and the reliability of microbe-mediated stress acclimation. The review identifies predictive understanding of context dependency, long-term field experimentation, standardised functional measurements and integration of rhizosphere processes into crop breeding and carbon models as the principal priorities. Rhizosphere biology offers genuine opportunities for sustainable and climate-resilient systems, but realising them requires management grounded in ecological mechanism rather than product-driven optimism.