Using microsatellite markers to map genetic diversity and population structure of an endangered Moroccan endemic tree (Argania spinosa L. Skeels) and development of a core collection

The aim of the present study is to examine the genetic diversity and relationships of natural populations of Argania spinosa based on inter-simple sequence repeats (ISSRs) and simple sequence repeats (SSRs). A total of 480 trees from 24 natural provenances of this species were sampled from southwest and northwest Morocco. Ten ISSR primers generated a total of 151 bands of which 150 were polymorphic (99%). Four primer pairs of SSR markers amplified 172 allelic variants among the argan genotypes with 100% polymorphism. Cluster analysis based on unweighted pair-group, principal coordinate, and Bayesian-based analyses, showed that the entire provenances were divided into two main groups for both markers used. The first group contained 22 provenances of southwest regions. The second cluster included the two relic provenances of Oued Grou and Beni Snassen. There was no significant correlation between genetic distance and geographic distance. Intermicrosatellites showed a high level of genetic differentiation among provenances (Gst = 0.44) while microsatellites presented moderate genetic differentiation. Based on genotyping data of ISSRs and SSRs, the constructed core collections consist of 13 and 96 genotypes representing, respectively, 2.7% and 20% of the entire A. spinosa collection. One hundred percent of the alleles present in the whole collection were present in the core sets. Our results provide an effective aid for future germplasm conservation, management strategies, and genetic association studies.