Genetic diversity in Mentha cervina based on morphological traits, essential oils profile and ISSRs markers

Morphological, phytochemical and genetic differences were studied to evaluate the level and distribution of diversity in twelve populations of the Portuguese endangered medicinal plant Mentha cervina L. Morphological variation was correlated with ecological conditions at the site of origin. Pulegone was the major essential oils compound in all of the populations collected at full flowering (68-83%), in different growing conditions (51-82%), and for all the developmental stages studied (47-82%). Although clusters were defined, the analysis revealed a high chemical correlation among all populations (Scorr ≥ 0.95%). Inter-simple sequence repeats markers were used to assess the population structure and genetic variation. Populations exhibited a relatively low genetic diversity (PPB = 14.3-64.6%, He = 0.051-0.222, I = 0.076-0.332), with high structuring between them (GST = 0.51). However, the genetic diversity at species level was relatively high (PPB = 97.7%; He = 0.320). The levels and patterns of genetic diversity were assumed to result largely from a combination of evolutionary history and its unique biological traits, such as breeding system, clonal growth, low capacity of dispersion and habitat fragmentation. The relatively low genetic diversity in the populations analyzed indicates that the maintenance of their evolutionary potential is at risk if population sizes are maintained and if there is no protection of the habitats.