Current evidence links microbial biogeography with grape condition, fermentation communities and wine chemistry, but much of that evidence is observational and strongly confounded by geography, climate, cultivar and management. These factors complicate efforts to distinguish microbial contributions from correlations associated with environmental or agricultural differences. The 50 questions span nine thematic domains, including vineyard soil ecology, holobiont assembly, plant–pest–microbe interactions, microbial product viability, circular-economy strategies, climate resilience, digital technologies and socio-economic implementation.

Across these areas, the synthesis calls for investigation of multi-domain microbial mechanisms associated with nutrient cycling, disease suppression, stress resilience, grape yield and grape quality. It also prioritizes assessment of how management practices and global change affect microbiome stability. These are proposed areas for research, not findings that the opinion paper demonstrates through vineyard experiments, and the survey does not establish the effectiveness of a particular microbial intervention.

The agenda extends from basic biological questions to the practical and institutional steps needed to translate microbiome research into scalable solutions for vineyard regeneration and sustainable wine production. Proposed directions include determining the viability of microbial products, identifying circular-economy strategies, examining climate resilience, considering the role of digital technologies and assessing socio-economic implementation. The authors present these topics as interconnected parts of a coordinated framework, intended to support discovery and innovation while helping align research with wider soil-health and climate strategies.

Its principal contribution is thus a structured international roadmap: 50 questions that clarify what grapevine microbiome science must resolve before microbiome-based approaches can be integrated into sustainable viticulture.

Subject of Research: An expert research agenda for grapevine microbiome science and sustainable viticulture

Article Title: Fifty fundamental questions to unlock the grapevine microbiome for sustainable viticulture

Article References: Ochoa-Hueso, R., Liberal, I. M., Aguiar, J. F., Alfaro, F., Alguacil, M. D. M., Belda, I., Blanco-Pastor, J. L., Bonanomi, G., Campos, V. E., Cantos-Villar, E., Casimiro-Soriguer, R., Cruz, C., Delgado-Baquerizo, M., Díaz-Losada, E., Dittrich, F., Edwards, R., Fiera, C., Foschino, R., García-López, A. M., … Revillini, D. (2026). Fifty fundamental questions to unlock the grapevine microbiome for sustainable viticulture. Plant and Soil. https://doi.org/10.1007/s11104-026-09170-7

Image Credits: AI Generated

DOI: 10.1007/s11104-026-09170-7

Keywords: grapevine microbiome, sustainable viticulture, research priorities, vineyard soil ecology, holobiont assembly, microbial biogeography, nutrient cycling, disease suppression, climate resilience, microbial products, circular economy, expert survey

The collection is organized around four themes, and the first concerns a deceptively simple question: how do microbial communities respond when their environment is stressed? The answer, according to the assembled studies, is that responses are highly uneven and context-dependent. In tropical oil palm plantations, fungal succession during litter decomposition was shown to control the release of nitrogen and the ability of roots to acquire it, illustrating how decomposer communities underpin nutrient cycling even in managed ecosystems. In the liverwort Marchantia polymorpha, human disturbance of habitats shifted fungal endophyte communities toward phosphorus-acquiring functional traits, an apparent adaptive response to nutrient limitation.

Resilience, rather than collapse, was the story in other systems. Sediment microbial communities in a mangrove estuary remained relatively stable despite fluctuating external conditions, reflecting an inherent robustness to environmental change. In farmland, a maize-soybean rotation under drip fertigation was dominated by ammonia-oxidizing microorganisms, including comammox bacteria, which significantly shaped nitrogen cycling in the soil. Meanwhile, drought and shifting soil moisture restructured the rhizosphere microbiomes of maize, common beans and peanuts, changes that appeared to help the plants manage water stress. Together, these studies provide an ecological foundation for the idea that microbiome-mediated stress adaptation is a general phenomenon, not a laboratory curiosity.

The second theme moves from ecology to mechanism: how exactly do microbes promote plant growth and stress tolerance? Several papers converged on a sobering conclusion for the biofertilizer industry. The effectiveness of microbial inoculants depended largely on the nutrient status of the soil, meaning that a product that works brilliantly in one field may fail in another. This points toward site-specific microbial interventions rather than one-size-fits-all formulations. Nutrient management itself was shown to shape microbial function, with banded application of ammonium polyphosphate enhancing phosphorus availability, bacterial diversity and maize productivity, while long-term fertilization experiments revealed that climate and fertilizer inputs jointly regulate microbial carbon and phosphorus limitation.

Some of the most striking results involve seed priming and quality enhancement. Coating chickpea seeds with the fungus Trichoderma asperellum reshaped the rhizosphere community, enriching free-living nitrogen-fixing bacteria and improving nitrogen uptake in the offspring plants even under salinity and pathogen pressure. In tea, a bio-organic fertilizer based on Bacillus megaterium improved crop quality by stimulating the biosynthesis of amino acids and flavonoids through microbiome-mediated regulation. Arbuscular mycorrhizal fungi emerged as versatile defenders, mitigating arsenic toxicity through multiple physiological and molecular mechanisms, while novel Pseudomonas isolates showed promise for promoting eucalyptus growth under environmental stress. A review of plant growth-promoting fungi rounded out the picture of how fungal partners can enhance plant fitness across systems.

The third theme tackles biotic stress, the constant threat posed by pathogens. One particularly elegant study in pigeonpea showed that volatile organic compounds produced by Bacillaceae bacteria from the rhizosphere reduced Fusarium wilt through two routes at once: direct antifungal activity against the pathogen and indirect priming of the plant’s own defenses. This dual mechanism highlights how chemical conversations between microorganisms can shape biocontrol, and it suggests that microbial metabolites themselves could become tools for crop protection, reducing reliance on synthetic fungicides.

Protection, however, is not only about single strains. Disease suppressiveness was shown to emerge as a property of entire microbial communities, with organic farming practices promoting rhizosphere microbiome configurations associated with enhanced general disease suppression in mustard. Environmental isolates of Pseudomonas suppressed the honey fungus pathogen Armillaria mellea while simultaneously promoting plant growth through microbiome-mediated effects. The implication is that plant protection operates across multiple levels, from specific antagonistic chemicals to community-scale suppression, and that farming practices which nurture diverse communities may quietly build disease-resistant soils.

The fourth and largest theme addresses abiotic stress, and here the range of crops and interventions is remarkable. Beneficial microbial inoculants and microbiota-enhancing amendments improved plant performance under water limitation in bell pepper, potato, pearl millet, coffee and lentil. In one visually compelling experiment, potato plants inoculated with the arbuscular mycorrhizal fungus Glomus or with Bacillus species grew markedly better under drought-induced soil water deficit than non-inoculated drought-treated plants, approaching the vigor of controls grown under optimal conditions. Other combinations proved synergistic: in lentil, silicon application combined with non-rhizobial bacterial co-inoculation enhanced resilience to water deficit, while in pearl millet, copper oxide nanoparticles paired with plant growth-promoting rhizobacteria boosted drought tolerance.

Salinity and soil degradation received equal attention. Bacterial inoculation improved the phytoremediation of saline soils by Atriplex nummularia, and iron-modified biochar enhanced cotton growth in saline-alkali soil by reducing salinity and facilitating root colonization by beneficial bacteria. Waste-derived amendments also played a role: black soldier fly larvae frass combined with wheat straw biochar supported bell pepper growth, soil fertility and rhizosphere bacterial communities under water stress. Even the environmental footprint of irrigation technology came under scrutiny, with biodegradable film drip fertigation shown to reduce the diversity and abundance of antibiotic resistance genes in soil compared with plastic film systems, a reminder that agricultural microbiomes are shaped by every input and practice.

The outlook offered by the editors is cautiously ambitious. Key challenges remain in predicting microbiome function across environments, translating laboratory findings into robust field applications, and scaling solutions across crops and production systems. Yet the collective evidence points toward a shift from merely describing microbiome ecology to actively harnessing it, integrating microbial ecology with nutrient management to build resilient and productive cropping systems. The special issue’s Marschner review goes further, recommending systems-level integration of plant microbiome engineering, metabolic innovations, tailored agronomic practices and supportive policy frameworks. If that integration succeeds, the invisible communities in the world’s soils may become one of agriculture’s most powerful allies against the environmental stresses of the coming decades.

Subject of Research: Use of soil and plant microbiomes to alleviate environmental stresses in agriculture

Article Title: Harnessing soil and plant microbiota to alleviate environmental stresses

Article References: Sharma, S., Jelsbak, L., Singh, A., Ghosh, A., & Lozano-Andrade, C. N. (2026). Harnessing soil and plant microbiota to alleviate environmental stresses. Plant and Soil. https://doi.org/10.1007/s11104-026-09128-9

Image Credits: AI Generated

DOI: 10.1007/s11104-026-09128-9

Keywords: soil microbiome, plant microbiota, drought stress, salinity, biofertilizers, biological control, arbuscular mycorrhizal fungi, plant growth-promoting rhizobacteria, sustainable agriculture, nutrient cycling, disease suppression, climate resilience