Biological nitrogen fixation is a process that provides a 65% anual nitrogen fixation ecosystem; executed by fungal microorganisms capable of reducing atmospheric form of N in an assimilable form. There are several human activities that have favored increasing addiction of N, which has led to the doubling of the amount of N that is incorporated by year in the different life cycles of the soil. This study aims to characterize molecularly and cryopreserved fungi associated with the stress response of N, soils subjected to high stress addiction sustained N with soil control, which cultivable fungi was isolated to be characterized and classified were selected morphologically through molecular techniques. Which resulted in 43 strains characterized by basic morphology (color, shape and size). By means of the sequence of the ribosomal ITS RNA gene, phylogeny indicated the presence of the phylum Ascomycota two clades. Eurotiales with the following genres (Penicillium, Citrinum, and Aspergillus). The Hypocreales clade presents the genera (Metarrhzium, Clonostachys and Tolypocladium) and Phylum Zygomycota with the genus Morlierella. The reactivation rate of the cryopreserved strains was 98%.
Keywords: Molecular characterization, cultivable fungi, ITS ribosomal RNA, Ascomycota, Zygomycota, cryopreservation.