Single or dual inoculation of arbuscular mycorrhizal fungi and rhizobia regulates plant growth and nitrogen acquisition in white clover

The present work aimed to analyse whether and how single or dual inoculation with arbuscular mycorrhizal fungi (Funneliformis mosseae, Paraglomus occultum, and Rhizophagus intraradices) and rhizobia (Rhizobium trifolii) improved plant growth and stimulated nitrogen (N) acquisition of white clover. AMF inoculation significantly (P < 0.05) increased root nodule number by 117-173%, and additional Rh considerably stimulated mycorrhizal growth. Single AMF or Rh treatment dramatically increased shoot by 36-281% and root biomass by 16-36% than non-inoculated control, and dual inoculation of Rh and P. occultum or R. intraradices further magnified the positive effect. Leaf and root N content, root total soluble protein content, root nitrogenase activity, and amino acid (e.g., alanine, arginine, asparagine, aspartate, phenylalanine, proline, and tryptophan) concentrations were significantly increased by single or dual inoculation, while dual inoculation of AMF and Rh had significantly superior roles than single corresponding AMF or Rh inoculation. These results suggested that AMF and Rh represented synergetic effects on accelerating N acquisition of white clover to some extent, while the combination of P. occultum and Rh was the best.