Metabolomics Uncovers the Mechanisms of Nitrogen Response to Anthocyanins Synthesis and Grain Quality of Colored Grain Wheat (Triticum aestivum L.)

Nitrogen (N) is a key factor for plant growth and affects anthocyanin synthesis. This study aimed to clarify the potential mechanisms of N levels (LN, 0 kg·ha–1; MN, 150 kg·ha–1; HN, 225 kg·ha–1) in anthocyanin synthesis and grain quality of colored grain wheat. HN increased the yield component traits and grain morphology traits in colored grain wheat while decreasing the processing and nutrient quality traits. Most quality traits were significantly negatively correlated with the yield composition and morphological traits. Anthocyanin was more accumulated under LN conditions, but other related yield and morphological traits of colored grain wheat declined. The anthocyanin content was the highest in blue wheat, followed by that in purple wheat. Cyanidin-3-O-(6-O-malonyl-β-d-glucoside) and cyanidin-3-O-rutinoside were the predominant anthocyanins in blue and purple wheat. The identified anthocyanin-related metabolites were associated with flavonoid biosynthesis, anthocyanin biosynthesis, and secondary metabolite biosynthesis. Therefore, the study provided information for optimizing nitrogen fertilizer management in producing high quality colored wheat and verified the close relationship between anthocyanin and low N condition.