Genetic diversity and population structure of wild Sardinian Myrtle (Myrtus communis L.) genotypes from different microclimatic areas

The wild Sardinian Myrtle (Myrtus communis L.) is an aromatic shrub widely spread in the Mediterranean region. Because of the large use of the plant in food and cosmetic industry a domestication process started in the last decades and today the myrtle may be considered an aromatic crop. In this evolution the genotype characterization of wild populations is essential to understand the bases of the phenotype variability useful for cultivar selection. The aim of the present study was to explore the genetic diversity and structure of wild myrtle populations within eco-geographical zone of Sardinia where the specie is still widely abundant. Eighteen populations were sampled randomly picking 20 individuals from every site. A total of 360 samples were analysed by AFLP markers revealing 150 polymorphic fragments. Two well-differentiated genetic groups were identified. Agrometeorological and geographical variables influenced the distribution of the two clusters. A significant different partition of the two groups was observed from South West to North East direction. Moreover, altitude plays a significant role in the genetic distribution: one cluster is predominant at low altitude and the other at medium (P = 0.0014). AMOVA was performed to explore the effect of different environmental factors to the genetic variance. The highest FST value (0.44) was associated to the origin of the sampling site followed by the genetic partition at K = 2 (0.34). A map of myrtle genetic diversity as result of the collection site was described. These findings are relevant for planning collection for future domestication program.