Owing to their symbiotic association with rhizobia, nitrogen-fixing woody legumes play a key role in the sustainability of many natural ecosystems and agro-ecosystems, particularly in the dry and arid regions of tropical and sub-tropical zones (Brockwell et al., 2005). Many studies have investigated the nitrogen-fixing status of legume trees from natural forests (Moreira et al., 1998; Diabate et al., 2005; de Faria et al., 2010) and agroforestry systems (Bala et al., 2003; Wolde-Meskel et al., 2005; Wang et al., 2006), particularly dry-zone Acacia species from Africa (Njiti & Galiana, 1996; de Lajudie et al., 1998; Haukka et al., 1998; McInroy et al., 1999; Ba et al., 2002; Odee et al., 2002) and Australia (Marsudi et al., 1999; Lafay & Burdon, 2001). In the case of Algeria, where the Saharan bioclimatic zone covers 89.5% of the total area in addition to 4.78% and 4.12% of arid and semi-arid regions, respectively (Nedjraoui, 2001), Acacia species appear as suitable candidates for thoughtful reforestation programs, with regard to their high resistance to salinity and drought (Brockwell et al., 2005) jointly with their ability to regenerate, stabilize, and fertilize soils through their nitrogen-fixing (Galiana et al., 2002, 2004) and mycorrhizal symbioses (André et al., 2005; Duponnois et al., 2007). In addition, they are considered as excellent sources of fuel, service wood, fodder, tannin, and medicines (Midgley & Bond, 2001). Acacia is a member of the Mimosoideae subfamily and is represented by about 150 species in Africa and 1100 species in Australasia (Maslin et al., 2003). The native Acacia species inventoried in Algeria, mostly distributed in northern and central Sahara, are A. ehrenbergiana, A. laeta, A. nilotica, A. seyal, and A. tortilis (Ozenda, 2004). Acacia species have also been introduced in Algeria, mostly along coastal areas such as Acacia saligna for dune stabilization and A. karroo that has been essentially planted as living hedges (El-Lakany, 1987), both species being exotics native to Australia and southern Africa, respectively. However, the distribution of Acacia species in Algeria remains poorly documented, and a precise cartography is still needed. Similarly, natural rhizobial symbionts of Acacia species have never been inventoried in Algeria so far except the recent publication on A. saligna by Amrani et al. (2010) restricted to bacterial populations from nursery soil. In their natural distribution area, most of the African Acacia spp. are associated with Mesorhizobium (de Lajudie et al., 1998; Haukka et al., 1998; McInroy et al., 1999; Ba et al., 2002; Odee et al., 2002), Ensifer (syn. Sinorhizobium) (de Lajudie et al., 1994; Lortet et al., 1996; Haukka et al., 1998; Khbaya et al., 1998; Nick et al., 1999b; Ba et al., 2002) and, to a lesser extent, Rhizobium (McInroy et al., 1999; Nick et al., 1999a) and Bradyrhizobium (Dupuy et al., 1994; McInroy et al., 1999; Odee et al., 2002). On the other hand, the Australian acacias are mainly associated with Bradyrhizobium (Galiana et al., 1990, 1994; Lafay & Burdon, 2001; Rodriguez-Echeverria et al., 2007; Le Roux et al., 2009; Perrineau et al., 2011). There is a major interest to inventory the biodiversity of introduced and native acacias and their associated rhizobia in Algeria to allow for effective selection of both symbiotic partners for use in reforestation programs. For this purpose, and as reported by Zhang et al. (1991) and Odee et al. (2002) in other arid and semi-arid regions, there is a need for inoculants that are able to survive to the stressful edaphic conditions found in Algeria. Recent field experiments performed on coastal dunes of West Algeria showed that the inoculation at nursery level of A. saligna seedlings with native rhizobia improved the survival of trees several months after transplanting (unpublished data). However, and this applies to the other Acacia species found in Algeria, the beneficial effect of inoculation on tree establishment and growth in field conditions requires the selection of indigenous rhizobia that are adapted and tolerant to high salinity and temperatures.