Integrated metabolomics and sensoryomics reveal scent diversification of 20 iris species for fragrance-targeted breeding

Iris is worldwide acknowledged as a fragrant flower and source of perfume, but the chemical composition and sensory characteristics of their fragrance remain poorly understood. This study analyzed the volatile compounds of 20 iris species, and investigated the volatile compounds of two iris species ( Iris. halophila pall. var. sogdiana (Bung) Grubov and I. uniflora Pall. ex Link) in particular in various flowering stages and flower organs using headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS). Meanwhile, sensory evaluation was conducted for the scent preferences, intensity, and types of the 20 species. The HS-SPME-GC-MS showed that fatty acid derivatives and terpenoid dominated the volatile compounds; and key volatile compounds identified included hexanal, ( E )-2-hexanal, 3-hexanal, 2-methyl-4-pentenal, 2-hexenal, linalool, methyl heptenone, oxime-methoxy-phenyl-, β-ocimene, ethyl caprate, and nonanal. Sensory evaluation confirmed that all the 20 iris species exhibited fragrance, and diverse composition of scent types. The combination of sensory evaluation and relative odor contribution (ROC) analysis indicated that 16 out of the 20 iris species have been identified with characteristic scent compounds. During the flowering period of the two specifically investigated species, the emission of volatile compounds initially increased and then decreased, peaking at the full bloom stage. For the emission of volatile compounds, the falls displayed the highest, followed by the standards and pistils. In this emission process, the osmophore along the petal margins played a significant role. The stamens emitted the least volatile compounds with a special composition. These findings provide valuable insights for the breeding of fragrant iris and the utilization of wild iris resources.