Introduction:

In the high mountain ranges of the Altiplano Potosino there are relict forests of Quercus spp. The species of ectomycorrhizal fungi associated with these ecosystems are so far unknown.

Objective:

To know the morphology of Astraeus aff. hygrometricus (Pers.) Morgan associated with Quercus species in three sites of scarce precipitation in the Altiplano Potosino.

Materials and methods:

Ectomycorrhizal fungi and vegetative structures of oak were collected during the rainy season for morphological characterization and identification. Soil physicochemical variables were evaluated by Tukey's analysis of variance and least significant difference (P = 0.05), to identify differences among the studied sites (Cerro El Peñon Blanco, Sierras de Guanamé and La Mojonera).

Results and discussion:

The ectomycorrhizal species A. aff. hygrometricus was associated with Quercus potosina Trel., Q. pringlei Seemen ex Loes., Q. tinkhamii C. H. Muller and Q. striatula Trel. The fungi had five to 14 laciniae per basidiomata and the following diameter ranges: 13 to 20 mm (endoperidium), 42.3 to 57.4 mm (exoperidium), 8 to 10.1 µm (spore length), 4.4 to 6.9 µm (endoperidium hyphae) and 4.9 to 9.2 µm (exoperidium hyphae). Oak and fungal species were found in friable soils (sandy to clayey) with pH 5 to 7.7 and low nitrogen (<2 %) and high phosphorus contents (85 mg∙kg-1).

Conclusion:

The ectomycorrhizal association of A. aff. hygrometricus with oak species explains the survival of these shrub oak forests under the semi-arid environments of the studied sites.