Multiomics analyses provide insights into the genomic basis of differentiation among four sweet osmanthus groups.

Sweet osmanthus (Osmanthus fragrans) is famous in China for its flowers and contains four groups: Albus, Luteus, Aurantiacus, and Asiaticus. Understanding the relationships among these groups and the genetic mechanisms of flower color and aroma biosynthesis are of tremendous interest. In this study, we sequenced representative varieties from two of the four sweet osmanthus groups. Multiomics and phylogenetic analyses of varieties from each of the four groups showed that Asiaticus split first within the species, followed by Aurantiacus and the sister groups Albus and Luteus. We show that the difference in flower color between Aurantiacus and the other three groups was caused by a 4-bp deletion in the promoter region of carotenoid cleavage dioxygenase 4 (OfCCD4) that leads to expression decrease. In addition, we identified 44 gene pairs exhibiting significant structural differences between the multiseasonal flowering variety "Rixianggui" in the Asiaticus group and other autumn-flowering varieties. Through correlation analysis between intermediate products of aromatic components and gene expression, we identified eight genes associated with the linalool and α- and ß-ionone biosynthesis pathways. Overall, our study offers valuable genetic resources for sweet osmanthus, while also providing genetic clues for improving the flower color and multiseasonal flowering of osmanthus and other flowers.

Assessment of genetic diversity and relationships among osmanthus fragrans cultivars using AFLP markers

This study was conducted to reveal genetic diversity among 100 Osmanthus fragrans cultivars using amplified fragment length polymorphism (AFLP) markers. Eight AFLP primer combinations produced a total of 443 polymorphic fragments with an average of 64 per primer combination. The percentage of polymorphic bands (86.81 percent), the resolving power (Rp) (32.71) and the PIC values (0.331) showed the efficiency of used primer combinations. The revealed AFLP makers were effective in distinguishing all the cultivars considered. Cluster analysis were performed to assess patterns of diversity among cultivars and showed the abundant genetic diversity. The overall distribution pattern of molecular variation suggested that 93.33 percent of the total genetic variance was within the identified groups and 6.67 percent of the genetic variation was among the identified groups. Our results showed that AFLP markers are useful for Osmanthus fragrans germplasm discrimination as well as for investigation of genetic diversity and variation. The information will facilitate germplasm identification, conservation and new cultivar development.