Rhizosphere Microbiome-Mediated Drought Resilience in Cereals: Implications for Grain Nutrition, Yield, and Tolerance.

Drought-mediated declines in grain nutritional quality and cereal yield put global food security at risk, yet the rhizosphere microbiome provides an alternative solution for improving crop tolerance. Our review synthesised existing knowledge on how soil microbiomes, particularly arbuscular mycorrhizal fungi (AMF) and plant-growth-promoting rhizobacteria (PGPR), simultaneously regulate three interlinked pillars of crop performance (stress tolerance, grain nutrient uptake, and yield) under drought. Our in-depth analysis showed that such relationships were governed by synergies (improved root architecture improves all three traits) and trade-offs (i.e., ABA-induced stomatal closure improves water efficiency but restricts carbon assimilation). Furthermore, these relationships were governed at different biological layers through multi-omics (metagenomics, transcriptomics, proteomics, and metabolomics) to identify biomarkers and pathways. With the application of an integrated framework through bioinformatics, it is now possible to reveal the hidden molecular layout between cereals and their underground partners, identify drought-responsive pathways, and discover biomarkers (nutrient transporter gene, microbial abundance, osmolyte accumulation, and root exudates). Despite advancements, critical technical gaps hinder data integration and standardised pipelines to identify complex traits through heterogeneous databases of omics. Our review proposes an integrated framework linking multi-omics tools, microbiome traits, and crop outcomes. Furthermore, we provide a research roadmap prioritising drought biofortification, synthetic communities (SynComs), microbial consortia, and spatial omics. Such research directly supports hidden hunger and food security agendas, while progressing climate-resilient agriculture.