Basil cultivar identification using chemotyping still favored over genotyping using core barcodes and possible resources of antioxidants

Ocimum sp. taxonomy and nomenclature are in a state of confusion; thus species and cultivar identification are hampered by the large number of species belonging to this genus. In this study, we examined DNA barcoding and leaf essential oil (EO) composition methods for cultivar identification of local and recently introduced Ocimum sp. Both barcodes of rbcLa and matK were sequenced for each species in parallel with leaf EO composition analyses using gas chromatography and GC-mass spectrometry (GC-MS) of five Ocimum basilicum cultivars. Antioxidant activities for the EO were determined using 2,2 '-diphenypicrylhydrazyl (DPPH) and beta-carotene-linoleic acid assays. The main EO constituents were methyl cinnamate (43.8%) in O.basilicum L., chavicol methyl ether (39.1% and 32.3%) in O.basilicum purple ruffle and anise; respectively, and linalool (30.9% and 30.6%) in O.basilicum Genovese and bush green, respectively. All cultivars were classified into chemotypes easily using their EOs when compared with barcoding using core barcodes, which exhibited no variation among all species in both markers except for Ocimum americanum, varying in a single base pair in matK. We concluded that chemotyping performed better than barcoding in species and cultivar identification, and the search for a better barcodes should continue.