Objective Changes in metabolic substances at various developmental stages of mulberry fruits were studied.

Methods  A widely targeted metabolomic analysis was conducted on Morus alba cv. yueshen dashi fruits sampled at the stages of green fruit, color transition, and maturation. KEGG metabolic pathway enrichment was analyzed based on the differentially accumulated metabolites (DAMs).

Results A total of 1 146 metabolic substances were identified from the specimens at the fruit developmental stages. At P＜0.05 and VIP＞1.0, 483 metabolites were identified as DAMs, 51 DAMs showed significant differences in the accumulation throughout the whole fruit development process. The contents of two flavonoids and one anthocyanin increased significantly during the developmental stages. The DAMs based on the KEGG metabolic pathway analysis indicated α-linolenic acid and linoleic acid metabolisms to be significantly enriched from the green to the colored stage, while ascorbate and aldarate metabolisms significantly enhanced from the color transition period to maturity, whereas linoleic acid metabolism as well as cutin, suberine, and wax biosynthesis significantly augmented throughout the entire development process. Although there were 6 up-accumulated and one down-accumulated linoleic acid, overall, the accumulation was on a downward trend as the fruits developed.

Conclusions There were 51 DAMs that might involve in the mulberry fruit development. It was found that anthocyanins and flavonoids rose significantly and 7 key metabolic components in the linoleic acid metabolism pathway might affect the quality and flavor of the fruits as well. The research results contributed a better understanding of the dynamic change in the nutritional composition of ripening mulberries, laying the foundation for revealing the mechanism of quality and flavor formation and breeding high-quality germplasm. At the same time, it also provided a scientific basis for determining the optimal fruit picking time.