Occurrence of spores of arbuscular mycorrhizal fungi in Agroforestry Systems and at the Manaus refinery, Amazonas State

The Amazonian soils are characterized by being weathered and presenting low natural fertility and high acidity. With these conditions, the cultivation of species of economic interest becomes a challenge. Arbuscular Mycorrhizal Fungi (AMF) form symbiotic associations with the roots of most vascular plants, aiding in the absorption of water and nutrients. The objective of this work was to evaluate the occurrence of spores of these fungi in the soils of three agroforestry systems and in an altered area of the Oil Refinery of Manaus Isaac Sabbá-REMAN. Samples were collected from rhizosphere soils of 21 host species. Per area, five specimens of each species with five replications were sampled. The spore density was determined using 30 g of rhizospheric soil from each plant following the wet sieving extraction technique and counting with the aid of a magnifying glass. Chemical attributes for soil macronutrients were evaluated. High concentrations of spores of arbuscular mycorrhizal fungi found in soils indicate that they are not a factor that can influence root colonization. Spores' numbers in the rhizosphere soils of the studied host species ranged from 248 to 687 in 30 g of soil and were influenced by management systems. The number of spores was significantly higher in AFS 3 than in AFS 1, AFS 2 and in the REMAN area. The soil under peach palm trees in AFS 3 showed the highest numbers of spores. Mycorrhizal-arbuscular fungi of the genus Glomus predominated in the study areas, followed by Acaulospora and Gigaspora.