American Journal of Plant Sciences, 2012, 3, 1294-1303 http://dx.doi.org/10.4236/ajps.2012.39156 Published Online September 2012 (http://www.SciRP.org/journal/ajps) Assessment of Genetic Diversity of Moroccan Cultivated Almond (Prunus dulcis Mill. DA Webb) in Its Area of Extreme Diffusion, Using Nuclear Microsatellites Abdelali Elhamzaoui 1,2 , Ahmed Oukabli 1 , Jamal Charafi 1 , Mohiéddine Moumni 2 1 Research Unit of Plant Breeding and Genetic Resources, Regional Agricultural Research Centre of Meknes, National Agronomic Research Institute, Meknes, Morocco; 2 Moulay Ismaïl University, Faculty of Science, Department of Biology, Zitoune, Meknès, Morocco. Email: oukabli2001@yahoo.fr Received May 8 th , 2012; revised June 5 th , 2012; accepted June 18 th , 2012 ABSTRACT Assessment of genetic diversity of Moroccan cultivated almond (Prunus dulcis Mill.) grown from seed and cultivated at four eco-geographical regions was performed using 16 nuclear SSRs. 238 alleles were detected with an average of 14.88 alleles per locus, ranging from 4 (locus BPPCT027) to 24 (locus CPSCT018). The size of alleles ranged from 84 bp (locus UDP96-003) to 253 bp (locus UDP96-018). A high genetic diversity of the local almonds is apparent and structured into three major clusters (Oasis cluster, High and Anti Atlas cluster, and Middle Atlas cluster). Compared to the Mediterranean genetic pools, from the East to West, the genetic diversity tends to be limited in Morocco which is the area of its extreme diffusion. Keywords: Almond; Genetic Diversity; Polymorphism; Spatial Genetic Structure; Prunus dulcis; Microsatellites; SSR 1. Introduction The almond [Prunus dulcis (Miller) DA Webb, syn. Prunusamygdalus Batsch] is a widely grown fruit tree that is commercially important throughout the world. It is native to mountainous regions of Central Asia [1,2] and is probably the oldest domesticated fruit tree in the third millennium BC [3]. The almond tree was spread from its origin through the Mediterranean by the Phoenicians, Greeks and Romans in three main dispersion routes: the north route, the southern route and the route through the seas [4,5]. The cultivated almond tree was introduced in the Me- diterranean region during the second millennium BC [6,7] with a broad exchange of almond in the fourth century BC [8]. It led to the differentiation between two groups, the Mediterranean species and species of Central Asia [2]. It evolved slowly by seeding to the nineteenth century [1] and its culture, in the region, is often associated with seedling populations with selection of local varieties in some countries [9]. This mode of propagation by seed- ing generated a great variability in local genotypes. Therefore, the Mediterranean region is regarded as a se- cond source of domestication of the almond [5,10,11]. Morocco is an area of extreme diffusion of the almond tree. It was cultured by the Carthaginians in the fourth century [12] as well as by the Arabs in the sixth century [10]. Almond culture is currently about 146,000 ha [13] of which less than half (about 4 to 5 million trees) con- sists of populations grown from seed, localized mainly in the south [14]. This sexual propagation has led to high genetic diversity and the country is now considered as a secondary center of almond diversity [15]. Several works on collection and morphological characterization were performed on these populations [16-19]. This traditional plant material, resulting from many centuries of adapta- tion, may provide a basis for an almond breeding pro- gram. A collection that grouped individuals from differ- ent regions of Morocco was installed at the experimental field of INRA in Aïn Taoujdate [19] for evaluation ef- forts. This collection possesses a genetic basis necessary for any breeding program. Genetic characterization of plant material is necessary for the identification of poten- tial genitors and their value in a breeding program. For the optimization of crossing schemes, the molecular characterization of this plant material is essential. Morphological characters were used in phenotypic ob- servations to characterize the genetic diversity of almond species, but their interactions with the environment and the small number of characters [20-22] prompted the use of other more discriminating techniques. Currently, DNA markers are widely used in studies of genetic diversity Copyright © 2012 SciRes. AJPS