Mapping knowledge on Arbuscular Mycorrhizal Fungi in the Amazon rainforest: a systematic review of diversity, distribution and symbiotic interactions

ABSTRACT The Amazon rainforest is one of the main global biodiversity hotspots where its diverse plant community provides optimal conditions and habitats for several soil microorganisms. Among these, Arbuscular Mycorrhizal Fungi (AMF) establishes important symbiotic relationships with many species of plants. We carried out a systematic bibliometric review of AMF in the Amazon, the mycorrhizal status of plant species, and a detailed analysis of the distribution of studies and occurrences of AMF species in Amazonian countries. The 110 studies examined had substantial spatial disparity, with research initiatives clustered in particular regions of Brazil and Peru, while information was totally absent for many Amazonian regions, including some countries in their entirety. The compiled studies encompassed 164 sampling sites in only 22 of the 55 Amazonian ecoregions. Furthermore, our analysis identified that most research focus was on assessing root colonization, morphological diversity, and spore quantification. These studies documented 143 AMF species, with the family Acaulosporaceae being most prevalent, and we highlight the description of 12 new species and four new genera from the Amazon. Only 181 plant species in 55 families were evaluated for symbiotic potential, of which 49 species (most in the Lecythidaceae) had no mycorrhizal association. This review underscores the necessity for expanded geographical coverage in inventories of Arbuscular Mycorrhizal Fungi, implementation of molecular approaches to expedite diversity assessment, and increased focus on plant-fungal symbiotic interactions throughout the Amazon.