Variability of Natural Populations of Atriplex Halimus L. in Morocco as Investigated by RAPD Markers

Atriplex halimus L. (Chenopodiaceae) is a monoecious C-4 perennial shrub native to the Mediterranean Basin, used as fodder shrub for livestock and useful for rehabilitation of degraded rangelands. To assess the levels and patterns of genetic diversity of this species, 99 samples of 11 populations collected throughout the natural range in Morocco plus 9 samples obtained from one population originating from USA, were analyzed using RAPD method and markers. A number of 157 reproducible amplified bands were obtained with 17 primers. Out of 157 amplified bands, 146 (93%) were polymorphic, and only 11 (7%) monomorphic. Global AMOVA analysis showed that the most genetic variation was within populations (66.57%), with the reminder occurring between populations (33.43%). Hierarchical AMOVA analysis revealed that variation among regions (Morocco versus USA) accounted only for 5.87% of the total genetic variation, suggesting that there is not a significant genetic differentiation of populations located at the opposite sides of the Atlantic Ocean. The actual genetic structure could have arisen by a combination of genetic drift effect and limited level of gene flow (0.50). The genetic diversity maintained by this species (0.238) was somewhat higher in comparison to other species with similar life histories and ecological traits. A neighbour- joining dendrogram based on Dice's coefficient resolved five major groups of populations correlated in part with bioclimatic type. Nevertheless, geographic distance did not explain the genetic differentiation among populations (r = 0.103, P = 0.646). The data obtained in this study should have important implications for the conservation and management strategies of genetic variation of Atriplex halimus in Morocco.