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Morphological variability and genetic relationships among basil (Ocimum sp.) accessions.

The genus Ocimum, containing between 30 to 160 species is widely cultivated as a source of essential oil for use in foods, flavors and fragrances as well as a culinary herb, spice and garden ornamental. High levels of both morphological and chemical variability exist within the genus. The taxonomy of Ocimum is somewhat confused due to interspecific hybridization, polyploidy, and the existance of chemotypes or chemical races that do not differ significantly in morphology. The 30 accessions that represented 6 species of Ocimum were analised. Preliminary descriptor list for Ocimum was developed comprising 36 easili scorrable morphological traits. Simple matching coefficient among accessions were calculated and clustering was carried out by UPGMA method using morphological data. RAPD markers were used to evaluate the genetic relationships among the accessions. Genetic distances were estimated via the coefficient of Jaccard and UPGMA cluster analysis was performed. The dendogram obtained indicates separation into five clusters. First, second, and third cluster containing O. tenuiflorum L., O. gratissimum L., and O. americanum L. accession respectively are good representation of traditional taxonomic relationships. Fourth cluster comprised O. x citriodorum Vis. accession as well as two O. basilicum var. purpurascens accessions from Russia. Two O. basilicum var. purpurascens accessions could in fact be of hybrid origin including O. x citriodorum Vis. as one parent, as its high crossability and high viability of progeny was readily observed by a number of authors. In fifth cluster different O. basilicum L. accessions were placed as well as three O. minimum L. accessions.it is possible that at genome level O. minimum L. is very similar to other O. basilicum taxa with rather limited number of dwarfing genes giving it clearly distinguishable morphological features.

Ocimum; morphological variability; genetic relationships; taxonomy

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