Distinct differences of rice grain quality caused by developmental stage and cultivar: A widely targeted metabolomics...

A widely-targeted metabolomics approach (UPLC-ESI-MS/MS) was employed to analyze the grain metabolites of three japonica rice cultivars-conventional white rice (CW), high resistant starch rice (RS), and purple rice (PR)-at 15 and 45 days after anthesis (DAA). A total of 1968 metabolites were identified. Multivariate analysis revealed that cultivar type exerted a stronger influence on the metabolome than developmental stage. A general metabolic remodeling pattern was observed, and significant enrichment pathways identified were nucleic acid-related pathways during rice grain maturation across all cultivars. RS was characterized by a sustained and broad up-regulation of terpenoids (n = 134 at 15 DAA, n = 124 at 45 DAA), whereas PR exhibited a concurrent up-regulation of flavonoids, terpenoids, lipids, and phenolic acids at both 15 and 45 DAA, with the number of up-regulated metabolites in each class exceeding 70. The metabolic advantage of RS might be linked to altered linoleic acid metabolism, whereas the metabolic identity of PR was derived from the co-activation of flavonoid, lipid and phenolic acid-related biosynthesis pathways at 45 DAA. This study reveals the cultivar-specific metabolic profiles of rice grown in the saline-alkali soils of the Yellow River Delta, offering valuable insights for the development of functional rice varieties suited to these regions.