Rosemary is an important crop for industrial production of essential oil. However, there is a significant effect of the genetic variation and the production process on the essential oil composition. Therefore, the present study was aimed at elucidating the effect of season and processing method on essential oil composition using the volatile structure of rosemary germplasm that was cultivated at the Newe Ya'ar research center for 30 years. Analysis of the essential oil composition of thirty-three germplasm identified four chemical groups: a '1,8-cineole' type, a 'verbenone' type, a 'camphor' type, and a 'α-pinene' type. Application of fractional factorial analysis of variance to the data indicated interactions of volatile by germplasm, volatile by method (hydro-distillation or solvent extraction), and volatile by season (summer 2017 or winter 2018), but not for germplasm by method, germplasm by season or method by season. This suggests that the germplasm was seasonally stable. Yet, the interaction between volatile by method pointed out that more camphor and 1,8-cineole were obtained by distillation, whereas more α-pinene was obtained by solvent extraction. Using four germplasm that were selected as chemo-type representatives for comparing hydro-distillation by Clevenger modified apparatus and steam-distillation, α-pinene was identified as a minor component in the hydrosol, whereas 1,8-cineole, camphor, borneol and verbenone were major components in the hydrosol. The outcome of the study reflects the importance of evaluating the effects of environment, genetic and processing methods on essential oil composition for accurate industrial breeding and production of essential oils.
Rosemary is an important crop for industrial production of essential oil. However, there is a significant effect of the genetic variation and the production process on the essential oil composition. Therefore, the present study was aimed at elucidating the effect of season and processing method on essential oil composition using the volatile structure of rosemary germplasm that was cultivated at the Newe Ya'ar research center for 30 years. Analysis of the essential oil composition of thirty-three germplasm identified four chemical groups: a '1,8-cineole' type, a 'verbenone' type, a 'camphor' type, and a 'α-pinene' type. Application of fractional factorial analysis of variance to the data indicated interactions of volatile by germplasm, volatile by method (hydro-distillation or solvent extraction), and volatile by season (summer 2017 or winter 2018), but not for germplasm by method, germplasm by season or method by season. This suggests that the germplasm was seasonally stable. Yet, the interaction between volatile by method pointed out that more camphor and 1,8-cineole were obtained by distillation, whereas more α-pinene was obtained by solvent extraction. Using four germplasm that were selected as chemo-type representatives for comparing hydro-distillation by Clevenger modified apparatus and steam-distillation, α-pinene was identified as a minor component in the hydrosol, whereas 1,8-cineole, camphor, borneol and verbenone were major components in the hydrosol. The outcome of the study reflects the importance of evaluating the effects of environment, genetic and processing methods on essential oil composition for accurate industrial breeding and production of essential oils.