Tracking an Introduced Arbuscular Mycorrhizal Fungus in Allium fistulosum in a Field Condition With or Without Controlling Indigenous Fungi by Soil Fumigation As Well as Evaluation on Plant Phosphorus and Growth

Increased plant phosphorus uptake and growth as a result of inoculation with arbuscular mycorrhizal (AM) fungi is observed less often under field conditions than in pot experiments. Interaction between introduced and indigenous AM fungi is one of the reasons for ineffectiveness of inoculation in the field. We aimed to distinguish the effect of introduced and indigenous AM fungi on phosphorus uptake and growth of Allium fistulosum in a field experiment. Superphosphate was applied in the ratio of 0 or 317 P kg ha −1 to the plots fumigated with or without dazomet that is a common soil fumigant. Seedlings of A. fistulosum that had been inoculated with or without Rhizophagus spp. strain R-10 were transplanted into the plots. AM fungal colonization, OTU read abundance of indigenous and introduced AM fungi, shoot P concentration, and shoot growth were measured at 31, 60, 90, and 131 days after transplanting (DAT). We could partially separate the effects of introduced AM fungi from indigenous AM fungi by fumigation with dazomet. Though neither inoculation nor P level affected shoot fresh weight and shoot P content in the non-fumigated main plot at 131 DAT, significantly higher shoot fresh weight was obtained by the inoculation with no P fertilizer in the fumigated main plot at this final sampling stage. These results indicate that the colonization of roots by introduced AM fungi is affected by the abundance of indigenous AM fungi and this interaction determines growth response of host plants under field conditions.