Genetic diversity of the endangered argan tree (Argania spinosa L.) (sapotaceae) revealed by ISSR analysis

Genetic variation in 150 trees of A. spinosa was estimated using inter-simple sequence repeat (ISSR). The plant material used in this study were originated from five provenances belonging to the principal provinces of argan ecosystem in southwest of Morocco. Based on the nine ISSR primers, 86 loci were scored. At the population level, percentage of polymorphic bands (PPB) was ranged from 75.58 to 82.56 %, Nei’s genetic diversity index (H) ranged from 0.30 to 0.34, Shannon’s information index (I) ranged from 0.44 to 0.49. Analyses of spatial genetic structure using UPGMA, the principal coordinate analysis and Bayesian-based approach from Structure program, showed that the entire provenances were successfully assigned to three groups. There was no significant correlation between genetic distance and geographic distance by Mantel test (r = 0.026, P = 0.942). The genetic differentiation coefficient (Gst = 0.22) was high, it was similar to the result of the analysis of molecular variance (28 % of the total variation among provenances). According to the genetic diversity results, the conservation and improvement strategies should be taking in consideration the provenance factor. So this study should be made appropriately the large sampling for the better representing of all diversity existing on the scale of the natural distribution of the argan.