E. Armada was financed by Ministry of Science and Innova- tion (Spain). This work was carried out in the framework of the project reference AGL2009-12530-C02-02. We would like to thank Domingo Álvarez by the morphological identification of autochthonous mycorrhizal fungus and the Service Microscopy (EEZ-CSIC) by the technique of TEM. We thank Dominic Paul Schmid (native English teacher) for their assistance in the revision of this work. And any thanks to Olga López and Francisca González for their collaboration in this work.