**4. AMF community composition associated with Argan trees**

The AM fungi are the important rhizospheric microorganisms whose diversity can be decisive for both plant community structure and ecosystem productivity. Studies on AMF occurrence and distribution have been made by spore extraction from soil and identification based on the morphology of the spores. Thus, the identification of spores has also been widely used to characterize AMF communities in soil [26, 37, 38].

#### **Figure 4.**

*Different structures of endomycorrhizal fungi colonizing the roots of Argania spinosa. Arbuscules (a); intra hyphae (ih), spores (s); vesicles (v) and endophytes (e). (G. × 400).*

#### **4.1 Root colonization with AM fungi**

The root colonization by AM fungi relies on the presence of microscopic structures, such as external and internal hyphae, vesicles and arbuscules, as well as endophytes (**Figure 4**).

#### **4.2 AMF spore density**

According to Morton *et al.* [39] and Sturmer and Bellei [40], spore density is the common tool for quantifying the AMF population in the soil. The highlighting of the structure mycorrhizal community consists of spores' number enumeration and abondance of each one. The communities of these fungi present in soil can be estimated in terms of the number of species observed and the abundance of each of them in the community. In *Argania spinosa* rhizosphere soil gathers 561 spores/100 g of soil (**Figure 5**) [41].

Oliveira and Oliveira [42] have revealed significant variations in spore density between the soil samples collected in August (dry season) obviously lower than in the sampling performed during the rainy season. Likewise, Khaekhum *et al*. [43] noted a higher number of AMF spores in the rainy season than in the dry season. The changes in spore densities are probably attributable to annual variations in climatic and edaphic conditions, especially as spore density increases in dry climates [44] reflecting adaptability to temperate, dry, and arid ecosystems [45, 46]. It is well known that edaphoclimatic conditions, such as pluvial precipitation can influence AMF spore density [47]. According to Pringle and Bever [48], fungal species sporulate differently on the season. For these authors, the seasonal variations in spore densities probably reflect seasonal differences in spore formation. Smith [49] showed that maximum spore densities are noted in the spring and decline in the summer.

The variation of spore density of AMF is directly related to the plant growth stage [50]. Various medicinal plants have displayed the highest intensity of AMF colonization and spore population in the flowering stage [51]. Hatimi and Tahrouch [52] have demonstrated that mycorrhization is nutrient level-dependent, and the spore production of AMF tends to be significant at the flowering stage and then decreased at the end of the growing season when the physiological cycle of plant roots changed. Indeed, disturbance of semi-arid ecosystems decreased mycorrhizal spore density and nutrient availability.

*Diversity of Arbuscular Mycorrhizal Fungi in the Rhizosphere of* Argania spinosa *in Morocco DOI: http://dx.doi.org/10.5772/intechopen.106162*

#### **Figure 6.**

*Some AMF species and morphotypes isolated from the rhizospheric soil of argan tree [41].*
