INFRASPECIFIC TAXONOMY AND ESSENTIAL OIL CHEMOTYPES IN SWEET BASIL, OCIMUM-BASILICUM

Essential oil compositions of fresh and freeze-dried leaves were deter mined for 16 accessions of Ocimum basilicum belonging to different var ieties to see whether they could be used as infraspecific taxonomic ch aracters. One accession of O. X citriodorum was also studied. Some 30 monoterpenoids, sesquiterpenoids and phenylpropanoids were identified, the major components (more than 20% of the total essential oil compos ition in one or more accessions) being geranial and neral in O. X citr iodorum, and linalool, methyl chavicol, eugenol, methyl eugenol and ge raniol in O. basilicum. Based on a combination of the latter compounds , five major essential oil profiles could be distinguished in the acce ssions studied for O. basilicum. These profiles were largely the same for fresh and freeze-dried material of the same plant, although in dri ed leaves, methyl chavicol and eugenol concentrations had generally de clined in comparison to those of linalool. There appeared to be little correlation between essential oil patterns and varietal classificatio n within O. basilicum. In view of the chemical heterogeneity of O. bas ilicum and its use as an essential oil-producing crop, culinary herb, medicinal plant and insect-controlling agent, in all of which chemical s play an important role, the infraspecific classification of this tax on should take chemical characters into consideration. A system for th e classification of essential oil chemotypes in O. basilicum is propos ed. Copyright (C) 1996 Elsevier Science Ltd