The objective of this study was to describe the morphological and anatomical features of five unidentified ectomycorrhizal types of Alnus acuminata and to complement their identification using ITS-DNA sequence analysis. The combined approach of morphotyping and sequence analysis based on ITS sequence comparison with sequences contained in GenBank and the UNITE database allowed us to assign three of the five field- collected ectomycorrhiza morphotypes to the tomentella-thelephora lineage that matched closely to European and North American species. The sequencing results within Tomentella point towards alder specific lineages within T. sublilacina, T. ellisii, and T. stuposa. The two other EcM morphotypes matched with Lactarius omphaliiformis and a Russula sp. Better focused, concomitant fruit-body surveys are needed for accurate identification of South American ectomycorrhizal fungi, because of the evidence of cryptic speciation events in both agaricoid and resupinate mycobionts.Fil: Pritsch, Karin. Helmholtz Zentrum München, German Research Center for Environmental Health, Institute of Soil Ecology; AlemaniaFil: Becerra, Alejandra Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Instituto Multidisciplinario de Biología Vegetal (p); Argentina; ArgentinaFil: Polme, Sergei. History Museum of Tartu University. Institute of Ecology and Earth Sciences and the Natural; EstoniaFil: Tedersoo, Leho. History Museum of Tartu University. Institute of Ecology and Earth Sciences and the Natural; EstoniaFil: Schloter, Michael. Helmholtz Zentrum München, German Research Center for Environmental Health, Institute of Soil Ecology, Department of Terrestrial Ecogenetics; AlemaniaFil: Agerer, Reinhard. Ludwig Maximilian University Munich (LMU), Department Biology I and GeoBioCenterLMU, Division of Organismic Biology: Mycology; Alemania