Arbuscular mycorrhizal fungal species differ in their capacity to overrule the soil's legacy from maize monocropping

Arbuscular mycorrhizal fungi (AMF) are promoted as biofertilizers for cleaner agricultural production. So far, most researchers have investigated the effects of AMF on plant growth under highly controlled conditions with sterilized soil. However, how the soil microbial community shapes AMF's impact on host plant performance is still poorly documented. To focus on the impact of belowground interactions (plant-AMF-soil microbes) alone, we compared sterilized versus non-sterilized soil, inoculating maize (Zea mays ssp. mays) seedlings with five commercial AMF inoculants (Claroideoglomus claroideum, Funneliformis mosseae, Gigaspora sp., Rhizophagus irregularis and Scutellospora sp.). Plants were pot-cultivated for nine weeks using soil which had been used for maize monocropping in the field. AMF inoculation was successful, despite an abundant native AMF community. As hypothesized: i) the soil microbial community interfered with AMF's benefits for maize growth; ii) these benefits depended on the AMF species, as C. claroideum, F. mosseae and Gigaspora sp. overruled the soil's legacy from maize monocropping. When plants were grown in sterilized soil, we found little to no effects of AMF inoculation on maize growth and nutrients acquisition. AMF's benefits to the host plants could not be explained by improved nutrition alone, since interaction with the remainder soil microbes also differed between inoculated AMF. Data show that the soil microbial community and AMF species should be taken into consideration when applying AMF inoculants in agriculture.