Untargeted Metabolomics of Xylem Sap Exudates in Two Common Bean Genotypes with Contrasting Growth Rates Under Water...

Background/Objectives: Water deficit during the pod filling stage severely limits the productivity of common beans (Phaseolus vulgaris). Although the effects of water scarcity have been extensively studied in leaves and roots, the contribution of xylem sap to systemic metabolic adaptation remains poorly understood. This study investigated genotype-specific metabolic changes in xylem sap exudates in response to water deficit in two common bean genotypes with contrasting growth rates. The OTI genotype has a growth cycle of 120 days, while Rosa La Bufa (RB) completes its cycle in 80 days under both well-watered and water deficit conditions. Methods: Physiological responses were evaluated, and xylem sap exudate metabolites were profiled using untargeted UPLC-ESI-QTOF-MS. Protein-metabolite interaction networks were reconstructed using STITCH v5 to identify genotype-specific metabolic organization under stress. Results: Water deficit reduced the abundance of multiple xylem metabolites, including flavonoids, isoflavones, phenolic acids, sugars, amino acids, and oxylipin-related compounds, indicating systemic metabolic contraction. OTI exhibited extensive metabolic changes characterized by enrichment of citrate, aromatic amino acids, glycolytic intermediates, flavonoid glycosides, and detoxification-associated metabolites, consistent with active carbon remobilization and oxidative stress responses. In contrast, RB accumulated isoflavones, including genistein, biochanin A, and baicalein, together with glycosylated triterpenoid saponins. Network analysis revealed that OTI developed a broad stress-responsive interactome that integrated phenylpropanoid metabolism, carbon remobilization, and detoxification pathways, whereas RB maintained a compact interactome reinforced by oxylipin-, jasmonate-, and isoflavone-associated modules. Conclusions: Xylem sap undergoes genotype-dependent metabolic adjustment under water deficit, suggesting contrasting drought adaptation strategies. Long growth cycle genotypes activate extensive metabolic plasticity, whereas reduced growth cycle genotypes rely on more specialized defense networks. These findings highlight xylem metabolomics as a valuable approach for understanding systemic drought adaptation and identifying putative metabolic biomarkers associated with drought resilience in common beans.