Arbuscular mycorrhizal fungi (AMF) are soil organisms that live as obligatory symbionts, forming an association with the roots of most plants, contributing to the regulation of the main terrestrial ecosystems by increasing the absorption area of nutrients in the soil, mainly phosphorus, allowing greater growth and tolerance to biotic and abiotic stresses, being, therefore, of great relevance for their maintenance. These ecological attributes show the importance of sustainable agricultural practices in addition to their potential use in the recovery of impacted areas.

Although the first AM fungi were described in 1844 ( Glomus macrocarpum Tul. & Tul. and G. microcarpum Tul. & Tul.), it was only in 1990 that AMF received special treatment, being grouped into their own order ( Glomales ) designated by symbiotic habit of these organisms (mycorrhiza formation). Before the last revolution in classification, these organisms belonged to the Mucorales , through the Endogonales and Glomales , all orders belonging to the Zygomycetes . During this period, taxonomy and classification were based almost exclusively on morphological evidence (similarity/difference of characters).

Currently, AMF constitute the phylum Glomeromycota, a group molecularly distinct from Zygomycota and phylogenetically closer to Ascomycota and Basidiomycota (groups more derived from fungi). However, this new classification system is based almost exclusively on molecular evidence (18s rDNA). Over the last 40 years, advances in the group's taxonomy had marked contributions during the 1970s, with the review by Gerdemann & Trappe (1974), in the 1980s, with descriptions of many new species, in the 1990s, with ontogenetic studies and at the beginning of the 21st century with the molecular revolution.

The entire taxonomic base used in this special group of fungi is related to the reproductive structure, called glomerospore, with the delimitation of taxa being extremely conflicting. Therefore, it is extremely significant for the group's taxonomy to disseminate the foundations (morphological characters related to the classification and identification of families, genera and species) of the systematics so that new evidence is quickly incorporated and allows the expansion of scientific knowledge.

In this context, the objectives of this page were (1) to show the morphological characters used in the taxonomy of the phylum Glomeromycota; (2) disseminate AMF species described and occurring in Brazil and (3) provide theoretical/practical support for the identification of families, genera and species of AMF.  

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