Constructed the metabolic compound accumulation profiles of daylily at different main producing areas using multi-omics techniques

Daylily flower buds (DFB) are widely cultivated in China. The discernible disparities exist in the nutritional composition of daylilies across different primary production areas. However, limited studies about the chemical composition and biosynthetic mechanisms of the principal constituents of DFB. This study systematically investigated daylilies from seven distinct growing regions by integrated metabolomics and transcriptomic sequencing to elucidate the environmental impact on DFB quality and metabolite biosynthesis mechanisms. In DFB, flavonoids constituting the majority, followed by phenolic acids and lipids. The total flavonoid and polyphenol content exhibited the highest levels in northern China (Ningxia, Gansu), and the lowest levels in southern regions (Hunan, Fujian). Correspondingly, antioxidant enzyme activity and free radical scavenging capacity mirrored these regional disparities. Thus, northern-producing areas demonstrated a propitious environment for the accumulation of secondary metabolites, particularly flavonoids and phenolic acids. In contrast, southern production areas exhibited a less conducive environment for the accumulation of flavonoid glycosides in daylilies. Furthermore, distinctive variations in the key metabolites were observed in FJQZ, a region characterized by diverse flower colors. Key enzymes and transcription factors were identified and validated through RT-qPCR. These results contribute valuable insights into the daylily quality formation mechanisms, offering a foundation for high-quality breeding strategies.