Integrated Microbiome and Metabolomics Reveal Mechanism of Saline–Alkali Stress in Avena sativa L.

Background/Objectives: This study subjected four-week-old oats (Avena sativa L. cv. Qinqiong and Avena sativa L. cv. Menglong) to saline–alkali stress for 6, 12, 24, and 48 h, and non-targeted metabolomics was used to analyse root metabolites under stress. Differential metabolites in oat roots after saline–alkali stress were primarily concentrated in substances such as carbohydrates, amino acids, acids, purines, and pyrimidines. Methods: In addition, 16S rRNA high-throughput sequencing was used to analyse changes in the rhizosphere microbial community structure of oats under saline–alkali stress. The abundance of some taxa, such as Nocardioides, Bacillus, and Proteobacteria, increased. Spearman’s correlation analysis was used to determine correlations between differential microorganisms and metabolites. Results: Oats can secrete carbohydrate substances into the rhizosphere to recruit strains such as Saccharothrix, Kineococcus, and Streptomyces; aliphatic and heterocyclic amino acid substances to recruit Arthrobacter, Bacillus, and Nostoc; and acid substances to recruit Accumulibacter, thereby alleviating saline–alkali stress. Conclusions: These findings are significant for further studies on saline–alkali resistance in oats and for exploring the potential of oats’ inherent saline–alkali resistance. They also provide basic data and theoretical and practical support for promoting the sustainable development of agriculture in saline–alkali soils through the utilisation of microorganisms and metabolites.