Patterns of Genetic Diversity and Structure at Fine Scale of an Endangered Moroccan Endemic Tree (<i>Argania spinosa</i> L. Skeels) Based on ISSR Polymorphism

Abstract

The preservation of the diversity of endangered populations of argan trees, in their natural habitat, is a crucial step toward their conservation. The aim of the present study was to evaluate the genetic diversity of the argan trees in the wild, and to establish a phylogenetic map using DNA fingerprints. The ultimate goal was to develop a core set that would represent the existing diversity in the whole germplasm. In regard to this, 200 samples of Argania spinosa individual trees were collected from 10 different provenances in the region of Essaouira (Morocco). The genetic variation between and within these argan trees was investigated using previously described Inter-Simple Sequence Repeat markers. These markers generated a total of 149 fragments, in which 148 (99.33%) were polymorphic. The samples collected in the ‘Ouled Lhaj’ provenance showed the lowest diversity (% of polymorphic locus P=48.32%; genetic diversity Nei h=0.153; allelic richness A=1.483), compared to those collected in the ‘Mramer’ provenance (%P=68.46%; h=0.233; A=1.685). Also, the results showed a high level of genetic differentiation among provenances (AMOVA=44%, Gst=0.40), and a limited gene flow (Nm=0.73) between the provenances. In addition, these data suggested a low correlation between the genetic diversity of the tree and their respective geographical location in relation to the proximity to the littoral. Finally, a core collection of 13 genotypes that represent the essential of the detected diversity was established. The distribution pattern of this genetic diversity provides an important baseline data for the conservation strategies of argan tree species in the wild.

Genetic, Morphological, and Biochemical Diversity of Argan Tree (Argania spinosa L.) (Sapotaceae) in Tunisia

“…In the present study, the 10 ISSR primers showed high levels of polymorphisms when compared to those revealed using different molecular markers on the same species, such as RAPD and allozymes analysis [6,14]. When comparing ISSR markers, the genetic diversity observed in populations of argan trees found within Tunisia is relatively similar to that of argan trees in Morocco [16,17,18,20]. Mouhaddab et al [17] showed that the genetic diversity based on Nei’s distance was between h = 0.153 and 0.233, which is still lower than the genetic diversity found between the different Tunisian sites.…”

“…When comparing ISSR markers, the genetic diversity observed in populations of argan trees found within Tunisia is relatively similar to that of argan trees in Morocco [16,17,18,20]. Mouhaddab et al [17] showed that the genetic diversity based on Nei’s distance was between h = 0.153 and 0.233, which is still lower than the genetic diversity found between the different Tunisian sites. However, if considering all the provenances that were studied as a single source, a high genetic diversity is noted (h = 0.353) which is almost similar to Nei’s genetic diversity found between Tunisian argans.…”

“…In order to adapt to and survive environmental changes, the genetic diversity of a species is vital; the higher the genetic diversity of a species, the higher its chance for survival in a changing climate. ISSRs are efficacious markers used to evaluate polymorphisms as well as the variability of many forest plant species including Argania spinosa [16,17,18,34,35,36,37,38,39].…”

“…The earliest research into the genetics of this species looked at isozyme markers isolated from chloroplast DNA using Polymerase Chain Reaction- Restriction Fragment Length Polymorphism (PCR-RFLP) [6,7]. Later, a study was published that used Random Amplified Polymorphic DNA (RAPD) [14,15], and Single Sequence Repeats (SSR) [15] as well as Inter-Simple Sequence Repeats ISSR Polymorphism [16,17,18] and Amplified Fragment Length Polymorphism (AFLP) [19], and more recently Inter Retrotransposon Amplified Polymorphism (IRAP) markers [20]. On the aforementioned techniques, ISSR presents the most consistent method of gene mapping, and yields the greatest number of polymorphic fragments per primer.…”

“…Essentially, this method allows for the identification of a high number of loci while using only a small number of primers [21]. ISSR markers have been proven successful for assessing the genetic diversity of many species, including Argania spinosa [16,17,18], barbary fig ( Opuntia ficus indica ) [22], Quercus infectoria [23], Cassia fistula L [24], Nothapodytes nimmoniana [25], and Myrciaria tenella [26].…”