Genetic diversity and structure of natural populations of Arbutus unedo across altitude, bioclimate and geographical origin as revealed by ISSR markers

In order to assess the genetic diversity and structure of Arbutus unedo species, 66 individuals’ trees from 11 natural populations representing its main geographical area in Morocco and belonging to different bioclimates and altitude were analyzed using 14 ISSR primers. A total of 142 bands were obtained, of which 134 were polymorphic with a polymorphism percentage of 94.06% and a polymorphism information content (PIC) of =0.47. The use of 134 markers revealed a high level of genetic variation within and between populations. The multi-locus values of Hs and Ht were 0.24 and 0.34, respectively. The overall AMOVA analysis showed that 79.30% of the total genetic variability was within populations and only 20.70% was between populations. A large genetic differentiation between populations was detected (FST=0.206) which could be attributed to restricted gene flow (Nm=0.97). The results of the hierarchical AMOVA, revealed very little genetic differentiation between altitudinal, bioclimatic and geographic groups (FCT=3.20%, FCT= 2.30% and FCT=2.10% respectively). Furthermore, geographic distances were revealed not correlated with genetic distances between populations (r=0.05, Mantel t-test=0.38, P=0.64) suggesting that isolation by distance has not played an important role in shaping the genetic structure of this species. The NJ dendrogram and Bayesian model-based clustering approach identified four groups of A. unedo independently of their bioclimate, geographic origin and altitude. The data obtained in this study could play a crucial role in establish efficient strategies for genetic resources conservation and to work out the scheme of breeding programs of A. unedo