Diversity of endomycorrhizal fungi on argan tree roots and potential for mycorrhizal development in the soil rhizosphere of argan stands in southwestern Morocco

Abstract

Argania spinosa, the argan tree, is endemic to Morocco and a key species in woodlands of outstanding interest that shape a unique agricultural landscape. While its mycorrhizal status has been extensively studied, the diversity and efficiency of associated mycorrhiza, taking the pedo-climate relationship into account as well as the diversity of argan habitats, is largely unknown. For this reason, this study investigated nine argan woodlands in south-western Morocco in order to (i) explore the diversity of mycorrhizal fungi communities associated with argan trees in different soil and climate conditions and (ii) assess the potential for the development mycorrhizal communities in rhizosphere environments, with a view to their use as sources of inocula. Microscope examinations of argan roots confirmed the mycotrophic character of the species and its dependence on arbuscular mycorrhizal fungi (AMF) in all the sites prospected. The AMF spores isolated from the soil rhi-zospheres in the argan stands studied are found in low densities. The correlations between the different morphotypes are very highly significant in the Glomus genus. For some sites, a positive correlation appears between the density of spores and the degree of root mycorrhization, while the mycorrhizal potential of the nine soils studied is negatively correlated with the chemical properties of the soils. These results suggest that other edaphic factors (e.g. biological soil properties), or soil disturbance in the argan stands due to farming or grazing, could strongly influence the mycorrhization process. This is the case with the performance of the mycorrhizal spores, which indicates a need to avoid counter-se-lecting AMF that are not effective in terms of argan tree survival and growth, whether the trees are grown in forestry nurseries or in the natural environment for woodland rehabilitation.