Comparative Quantitative Metabolomics Analysis of Nutritional Differences in Different Plant Parts of Oilseed Rape (Brassica napus L.) at the Bud Stage

In this study, quantitative nuclear magnetic resonance (NMR) spectroscopy and high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) were used to analyze the differences in the composition of small-molecule nutrients in different parts (stems, leaves and flower buds) of ‘Dadi 95’ oilseed rape (Brassica napus L.) at the bud stage. The results showed that 53 small-molecule compounds were identified and quantified in total. Among these, substances with significant differences were leucine, isoleucine, valine, γ-aminobutyric acid, alanine, proline, phenylalanine, lactate, citrate, succinamide, β-D-glucose, α-D-glucose, sucrose, fructose, choline, betaine, fumaric acid, baicalein, ferulic acid, kaempferol, sinapine, trans-cinnamic acid, and hesperetin. Comparative analysis revealed that the content of carbohydrate was the highest in the stem of B. napus L., whereas choline, succinamide, most of amino acids, organic acids, and phenolic acids were mainly accumulated in the buds, and the dominant metabolites in the leaves were baicalein, sinapine, and citric acid. Metabolic pathway analysis demonstrated that these differential metabolites were mainly involved in the citrate cycle, flavone and flavanol biosynthesis, phenylalanine metabolism, aminoacyl-tRNA biosynthesis, valine, leucine and isoleucine biosynthesis, glycolysis/gluconeogenesis, and phenylalanine, tyrosine and tryptophan biosynthesis in the plant. The results from this study provide foundational data for comprehensively assessing the nutritional value of B. napus L. at the bud stage, and a scientific basis for selecting and breeding nutritious oilseed rape varieties.