Efficiency of morphological trait descriptors in discrimination of Ocimum basilicum L. accessions K. CAROVIC ´ -STANKO 1 , A. S ˇ ALINOVIC ´ 1 , M. GRDIS ˇ A 1 , Z. LIBER 2 , I. KOLAK 1 ,& Z. SATOVIC 1 1 Faculty of Agriculture, Department of Seed Science and Technology, University of Zagreb, Croatia and 2 Faculty of Science, Division of Biology, Department of Botany, University of Zagreb, Croatia Abstract Most commercial basil cultivars belong to the species Ocimum basilicum L. Moreover, within O. basilicum species, there are five main botanical varieties (var. basilicum L., var. difforme Benth., var. minimum L., var. purpurascens Benth. and var. thyrsiflorum /L./ Benth.) that are mainly found on the market. High levels of both morphological and chemical variability exist within the species due to the intraspecific hybridization and long-term uses throughout the world. The aim of this work was to study the resolving power of morphological traits for reliable identification of basil accessions. Phenotypic dissimilarities between pairs of accessions were calculated, and the unweighted pair-group method dendrogram was constructed. Six clearly defined clusters have been detected, giving a good representation of traditional taxonomic relationships. To compare the efficiency of the morphological traits in accession identification, confusion probability and discriminating power of each trait were calculated. Our results show that with a careful analysis and stringent selection of traits, morphological markers provide an inexpensive and reliable method for routine screening of a large number of accessions, in order to monitor and manage germplasm collections. Keywords: Accession, basil, discriminating power, morphological traits, Ocimum basilicum Introduction The genus Ocimum L. (Lamiaceae) comprises annual and perennial herbs and shrubs native to the tropical and subtropical regions of Asia, Africa, Central and South America (Labra et al. 2004). For a long time, basil has been acclaimed for its diversity as a source of essential oils, its flavour and delicacy as spice and its beauty and fragrance as an ornamental (Simon et al. 1990). It is extensively used by the perfume, pharmacy and food industries for its natural aroma and flavour (Darrah 1980). Basil is used in tradi- tional ceremonial rituals and as medicines while it contains biologically active constituents that are antimicrobial (Lachowicz et al. 1998; Thoppil et al. 1998), insecticidal (Umerie et al. 1998), nematocidal (Vieira & Simon 2000) and fungistatic and antiox- idant (Politeo et al. 2006). High levels of both morphological and chemical variability exist within the basil due to intraspecific hybridization and the existence of chemotypes or chemical races that do not differ significantly in morphology (Simon et al. 1990). Most commercial basil cultivars available in the market belong to the species O. basilicum. Within O. basilicum species, there are five main botanical varieties: var. basilicum L., var. difforme Benth., var. minimum L., var. purpurascens Benth. and var. thyrsiflorum /L./Benth. Within the var. basilicum, there are two most popular cultivars ‘‘Genovese’’ and ‘‘Sweet Basil’’, while var. purpurascens includes cultivar ‘‘Dark Opal’’. Darrah (1980) classified the O. basilicum cultivars in seven types: (1) tall slender types, which include the ‘‘Sweet Basil’’ group; (2) large-leafed, robust types, including ‘‘Lettuce Leaf’’ also called ‘‘Italian’’ basil; (3) dwarf types, which are short and small leafed, such as ‘‘Bush’’ basil; (4) compact types, such as var. thyrsiflora, commonly called ‘‘Thai’’ basil; (5) purpurascens, the purple-coloured basil types with traditional sweet Correspondence: K. Carovic ´-Stanko, Faculty of Agriculture, Department of Seed Science and Technology, University of Zagreb, Svetos ˇimunska 25, 10000 Zagreb, Croatia. Tel: þ385 1 2393622. Fax: þ385 1 2393930. Email: kcarovic@agr.hr Plant Biosystems, Vol. 145, No. 2, June 2011, pp. 298–305 ISSN 1126-3504 print/ISSN 1724-5575 online ª 2011 Societa ` Botanica Italiana DOI: 10.1080/11263504.2011.558677