Combinations of different arbuscular mycorrhizal fungi improve fitness and metal tolerance of sorghum in ultramafic soil

Research on arbuscular mycorrhizal fungi (AMF) in ultramafic soils has principally focused on ecological restoration whereas little attention has been given to agriculture. The present study aims at understanding if mixtures of different AMF species from a New Caledonian ultramafic soil induced a better plant fitness and lower contents of potentially toxic metals in aerial parts of a crop plant than single species inoculants. Sorghum vulgare plants were inoculated using six AMF species separately and in different mixtures of these species in a glasshouse experiment in ultramafic soil. The tested inocula showed very different effects on plant fitness. Results highlight that, when sorghum is grown in ultramafic soil, AMF mixes were more efficient than single species inoculation in alleviating abiotic stresses by reducing translocation of potentially toxic metals to the aerial part of the plant and thereby improving the fitness of the plants. Our findings point out the utility of arbuscular mycorrhizal biotechnology for agricultural ultramafic soils. •Co-inoculation of arbuscular mycorrhizal fungi (AMF) improved fitness of sorghum.•Mixture of AMF reduced drastically metal contents in aerial parts of the plants.•AMF mix containing different taxa was more efficient than single species inoculant.•The best inoculum was a mix of three AMF species belonging to different families.