The aim of the present study is to evaluate the absolute content and accumulation patterns of flavonoid components; to give insight into the accumulation relationships among flavonoid components; to explore the correlation between the content of flavonoid components and the expression of flavonoid biosynthesis genes in Tartary buckwheat seeds; and to construct a biosynthetic pathway on the major flavonoid components in Tartary buckwheat seeds. In total, 61 flavonoid components were absolutely quantified in five Tartary buckwheat varieties, of which 41 existed in all varieties. The content of most flavonoids varied significantly among different varieties or within the same variety. Rutin, quercetin, nicotiflorin, and kaempferol were the dominant flavonoid components in the Tartary buckwheat seeds, accounting for 73.05–81.79% of the total flavonoids. Significantly positive or negative correlations with content accumulation were found between some flavonoid components. Thirty-six flavonoid components displayed four different accumulation patterns in the developing Tartary buckwheat seeds. Seventeen structural genes for flavonoid biosynthesis displayed a significantly positive correlation with the accumulation of most flavonoid components during the development of Tartary buckwheat seeds, and the F3′5′H-3 gene might be the most crucial contributor in determining the total flavonoid content in Tartary buckwheat seeds. A schematic of the biosynthesis pathways for 30 major flavonoids in Tartary buckwheat seeds was constructed. These findings provide an outlook of the flavonoid components and their biosynthesis in Tartary buckwheat seeds and have potential applications in breeding new cultivars with higher flavonoid contents.

Tartary buckwheat (Fagopyrum tataricum Gaertn.) is a coarse grain crop rich in flavonoids that are beneficial to human health because they function as anti-inflammatories and provide protection against cardiovascular disease and diabetes. Flavonoid biosynthesis is a complex process, and relatively little is known about the regulatory pathways involved in Tartary buckwheat. Here, we cloned and characterized the FtMYB163 gene from Tartary buckwheat, which encodes a member of the R2R3-MYB transcription factor family. Amino acid sequence and phylogenetic analysis indicate that FtMYB163 is a member of subgroup 7 (SG7) and closely related to FeMYBF1, which regulates flavonol synthesis in common buckwheat (F. esculentum). We demonstrated that FtMYB163 localizes to the nucleus and has transcriptional activity. Expression levels of FtMYB163 in the roots, stems, leaves, flowers, and seeds of F. tataricum were positively correlated with the total flavonoid contents of these tissues. Overexpression of FtMYB163 in transgenic Arabidopsis enhanced the expression of several genes involved in early flavonoid biosynthesis (AtCHS, AtCHI, AtF3H, and AtFLS) and significantly increased the accumulation of several flavonoids, including naringenin chalcone, naringenin-7-O-glucoside, eriodictyol, and eight flavonol compounds. Our findings demonstrate that FtMYB163 positively regulates flavonol biosynthesis by changing the expression of several key genes in flavonoid biosynthetic pathways.