Comparative Analysis of Flavonoids and Polar Metabolite Profiling of Tanno-Original and Tanno-High Rutin Buckwheat

Rutin is an important indicator for evaluating the quality of buckwheat. In this study, flavonoid biosynthesis was compared between two common cultivars (an original and a high-rutin line) of buckwheat, <i>Fagopyrum esculentum</i> Moench. Transcriptional levels of the main flavonoid biosynthetic genes were analyzed by real-time PCR, and main flavonoid metabolites were detected by high-performance liquid chromatography (HPLC); levels of gene expression varied among organs of the two cultivars. Significantly higher transcription levels of most flavonoid biosynthetic genes, except <i>FeFLS1</i>, were detected in stems of the high-rutin line than in stems of the original line. <i>FeCHI</i> and <i>FeFLS2</i> genes also showed higher expression levels in seeds of the high-rutin cultivar. In contrast, <i>FePAL</i>, <i>FeC4H</i>, <i>Fe4CL1</i>, <i>FeCHS</i>, <i>FeF3H</i>, <i>FeF3</i>′<i>H</i>, <i>FeFLS2</i>, and <i>FeDFR</i> were highly detected in the roots of the original line. The HPLC results indicated 1.73-, 1.62-, and 1.77-fold higher accumulation of rutin (the primary flavonoid compound) in leaves, stems, and mature seeds of the high-rutin cultivar (24.86, 1.46, and 1.36 μg/mg, respectively) compared with the original cultivar (14.40, 0.90, and 0.77 μg/mg, respectively). A total of 46 metabolites were identified from seeds by gas chromatography–time-of-flight mass spectrometry. The metabolite profiles were subjected to principal component analysis (PCA). PCA could clearly differentiate the original and high-rutin cultivars. Our results indicate that the high-rutin cultivar could be an excellent alternative for buckwheat culture, and we provide useful information for obtaining this cultivar