Establishment, persistence and effectiveness of arbuscular mycorrhizal fungal inoculants in the field revealed using molecular genetic tracing and measurement of yield components.

• Inoculation of crop plants by non-native strains of arbuscular mycorrhizal (AM) fungi as bio-enhancers is promoted without clear evidence for symbiotic effectiveness and fungal persistence. To address such gaps, the forage legume Medicago sativa was inoculated in an agronomic field trial with two isolates of Funneliformis mosseae differing in their nuclear rDNA sequences from native strains. • The inoculants were traced by PCR with a novel combination of the universal fungal NS31 and Glomeromycota-specific LSUGlom1 primers which target the nuclear rDNA cistron. The amplicons were classified by restriction fragment length polymorphism and sequencing. • The two applied fungal inoculants were successfully traced and discriminated from native strains in roots sampled from the field up to 2 yr post inoculation. Moreover, field inoculation with inocula of non-native isolates of F. mosseae appeared to have stimulated root colonization and yield of M. sativa. • Proof of inoculation success and sustained positive effects on biomass production and quality of M. sativa crop plants hold promise for the role that AM fungal inoculants could play in agriculture.