Comparative profiling and natural variation of polymethoxylated flavones in various citrus germplasms

Citrus fruits are the main dietary source of polymethoxylated flavones (PMFs) with significant effects on consumer health. In this study, eleven main PMFs were evaluated in the fruit flavedo or leaves of 116 citrus accessions via UPLC-DAD-ESI-QTOF-MS/MS combined with HPLC-DAD analysis, which revealed significant species-specific and spatiotemporal characteristics. All Citrus reticulata and their natural or artificial hybrids were found to have detectable PMFs, especially in the fruit flavedo of the wild or early-cultivated mandarins at early fruit development stages. However, PMFs were not detected in citrons, pummelos, kumquats, trifoliata oranges, papedas, Chinese box oranges and 'Mangshanyegan'. The results enlightened that PMF accumulation only in mandarins and mandarin hybrids is a phenotype inherited from mandarin ancestors. This study provides a comprehensive PMF profile in various citrus germplasms and will benefit future functional citrus breeding practices aimed at designing plants rich in total or specific PMFs for health benefits.