Background:

The elements that are toxic to arbuscular mycorrhizal fungi (AMF) and soil microorganisms, and the levels at which they affect them, are poorly known.

Objective:

To quantify the effects of: 1) aluminum added to the soil (0, 50 and 100 mg kg-1) and 2) inoculation with AMF (two isolates without prior exposure to aluminum, Acaulospora delicata and Gigaspora margarita, the native AMF community of a soil contaminated with Al, and a control without AMF) on the development of AMF mycelium and the hyphosphere-associated microbiota.

Methods:

A system with two compartments was used, a central compartment in which maize was sown and AMF were inoculated and a side compartment without root passage, where only the external mycelium was exposed to the different concentrations of Al. AMF external mycelium exposed to Al was quantified with the fatty-acid biomarker 16:1ω5.

Results and conclusions:

Al concentrations up to 100 mg kg-1, controlling the pH of the soil, did not alter mycelium growth of any of the inoculated HMA either in the soil or in the roots. Aluminum added up to 100 mg kg-1 did not have a direct toxic effect on the growth of AMF mycelium and the hyphosphere-associated microbiota.