Abstract

Essential oil of forty-five Ethiopian rosemary accessions was analyzed using gas chromatography-mass spectrometry (GC-MS) to investigate the variability of essential oil composition.A total of 42 compounds, representing 95.85-98.89% of the total oil composition were detected. The oils were dominated by α-pinene (5.08-40.62%), 1,8-cineole (8.13- 38.48%), camphor (2.15-23%), verbenone (1.83-20.25%), β-caryophyllene (2.12-9.39%), endo-borneol (1.79-12.56%), camphene (1.69-7.86%,), bornyl acetate (1.55-9.65%), limonene (1.65-6.07%), α-terpineol (1.66-6.37%), β-pinene (1.55-6.45%), and linalool (1.58-3.91%). Among these, α-pinene, 1, 8-cineole, camphor, and verbenone were the most ubiquitous constituents and found to present in all accessions, while the rest varied among the accessions. Correlation analysis showed that α-pinene, 1, 8-cineole and verbenone were correlated negatively with the majority of the major compounds, while the association of camphor with the entire main constituent was not significant, except with α-pinene (r = -0.46***) and linalool (r = -303*). Based on the relative concentration of the main constituents of the essential oils, six distinct chemotypes were identified for Ethiopian rosemary accessions. The chemotypes were: α-pinene/1,8- cineole/camphor; α-pinene/1,8-cineole/verbenone; α-pinene/1,8-cineole/endo-borneol; 1,8-cineole/camphor/α-pinene; verbenone/α-pinene/camphor and camphor/1,8-cineole/verbenone. The defined chemotypes demonstrated the presence of high chemical variability among individual plants that makes it difficult to describe a single chemotype based on geographic origin. Interestingly, more contribution of genotype for the chemical variability than environmental factor was noticed in the present study, indicating the inherent nature of the essential oil constituents. Overall, the observed high essential oil constituent variability among the tested accessions reflected the enormous potential of Ethiopian rosemary germplasm for wider applications in different destinations that are predominated by rosemary products.