Genetic diversity and population structure in natural populations of Tunisian Azarole (Crataegus azarolus L. var. aronia L.) assessed by microsatellite markers

• The genetic diversity of Tunisian Azarole populations was assessed by SSR markers.
• Relatively high levels of genetic diversity and population structure were revealed.
• Populations' divergence was independent to their eco-geographic appurtenances.
• The current critical status of natural Azarole habitats requires its conservation.

Azarole tree (Crataegus azarolus var. aronia) is a medicinal plant largely reported to possess a wide range of pharmacological properties. In Tunisia, the species grows wild in different bioclimates and geographic areas. It occurs in small scattered populations in continuously distributed habitats. In order to elaborate efficient conservation strategies of the species, nine SSR loci were used to estimate the genetic diversity and population structure of nine populations growing wild in different bioclimatic zones extending from the upper semi-arid to the lower humid.A relatively high level of genetic diversity within population was detected (Na = 2.889, Ne = 2.137, P = 65.43% and He = 0.386). The level of genetic diversity varied according to bioclimate. A low rate of heterozygotes was observed for all populations. The deficit of heterozygotes was more important for populations belonging to the upper semi-arid bioclimate. A significant differentiation among all populations (FST = 0.255; ΦST = 0.297), and among populations within bioclimatic stages (ΦSC = 0.288) were revealed. The Mantel test showed a lack of significant correlation between FST values and geographical distances among populations. The UPGMA and the Bayesian analyses did not show a relationship between population clustering and their eco-geographic appurtenances. Considering these results as well as the current situation of all populations and their endangered habitats, the conservation of this medicinal species is required.

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