Metabolic rewiring for nutritional enhancement in Tartary buckwheat grains: Reshaping quality along the domestication-to-improvement trajectory.

Tartary buckwheat is a nutrient-rich pseudocereal, yet the metabolic basis underlying quality shifts from domestication to breeding improvement remains poorly understood. Here, phenotyping together with untargeted and targeted metabolomics was integrated to characterize wild-type (WT), cultivated-type (CL), and newly developed (HB) germplasm, and machine-learning analysis was further used for a preliminary assessment of stage discrimination. HB showed larger grains and more pronounced metabolic remodeling than CL/WT. Targeted analyses revealed a V-shaped pattern for several flavonoids, with vitexin and isovitexin markedly enriched in HB. Trigonelline increased only slightly during domestication (WT → CL, +8.3%) but rose sharply during improvement (CL → HB, +164.05%). Validation across 30 accessions further supported that trigonelline accumulation was mainly associated with improvement rather than domestication. Among seven models, logistic regression performed best, although validation remained moderate (AUC = 0.69; accuracy = 70%). These findings define breeding-improvement-associated metabolic signatures and candidate metabolites for nutritional-quality-oriented Tartary buckwheat improvement.