Genetic diversity and population structure among Rosmarinus officinalis L. (Lamiaceae) varieties: var. typicus Batt. and var. troglodytorum Maire. based on multiple traits

Rosmarinus officinalis is the most used medicinal species in the Mediterranean region. It includes several botanical varieties and forms. Quantitative and genetic markers were used to assess the genetic diversity and genetic differentiation between eight natural Tunisian populations belonging to two allopatric varieties R. officinalis var. typicus Batt. and R. officinalis var. troglodytorum Maire endemic to Tunisia. The systematical position of the former has been recently questioned. The genetic differentiation among populations and varieties was assessed using flower traits (corolla length, pollen grain size, fertility and viability, style and stamen length), essential oil compounds, allozymes and RAPDs. The four sets of markers allowed similar patterns of high genetic differentiation among populations. PCAs performed on single or combined traits provided a good distinction among the two varieties with a high heterogeneity among var. typicus populations according to the bioclimate. The high differentiation among varieties arises from genetic drift and low level of gene flow among them due to habitat fragmentation. The recognition of both varieties should be maintained in the treatment of Tunisian R. officinalis. Conservation and improvement strategies should be made appropriately according to the variety and the bioclimate.

► In Tunisia, Rosmarinus officinalis L. comprises four botanical varieties.
► Floral, essential oil, allozyme and RAPD markers were used to asses the differentiation between the two varieties typicus and troglodytorum.
► A clear distinction between the two taxa was revealed by each set of markers.
► The differentiation among the two varieties results from low level of gene flow among them.
► The recognition of the two varieties should be maintained in the treatment of Tunisian Rosmarinus officinalis.