Composition analysis of floral scent within genus Camellia uncovers substantial interspecific variations

The great diversity and complexity of floral scent originate from specialized metabolic pathways partly due to the ever-evolving plant and pollinator interaction. However, the diversity of floral scent compositions in plant species remains to be elucidated. Genus Camellia contains a large number of species including several famous ornamental species, and species within the section Theopsis possess distinctive floral scent traits. In this study, we have collected 22 species from Theopsis and performed headspace-solid phase microextration coupled with gas chromatography mass spectrum (HS-SPME-GC-MS) analysis to investigate the scent compositions. In total, we identified 223 volatile compounds belonging to benzenoids, phenyl propanoids, terpenes, and other components. Remarkable interspecific variations in composition and quantity were revealed. We characterized the relationships of different types of volatile compounds by hierarchical clustering and principal component analysis, and showed that small amount of chemicals could affect the scent effects significantly. Moreover, we compared the volatile emission patterns between different floral organ types and developmental stages in Camellia boxifolia. We revealed that stamens emitted more volatiles than petals, and the emission reached the maximum at the stage of flower half opening. This work provides fundamental information for breeding Camellia cultivars with scent traits.