The present study was carried out to study the effect of inoculation with arbuscular mycorrhizal fungi (AMF) and some beneficial microbes under labeled nitrogen ( 15 N) fertilization on AMF root colonization and spore density of some medicinal plants. The occurrences of AMF diversity have been studied in rhizosphere soils of 22 medicinal plants in Sekem Company Farm, and the percentage of mycorrhizal colonization on each plant and the number of spores per 100g rhizosphere soil was calculated.

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... F was observed in almost all plants. There were great variations in AMF colonization based on host plant. The highest root infection was observed in black cumin plant, being 77% and the lowest was in parsley plant, being 18.17%. The highest spore population (368/100g rhizosphere soil) was recorded in anise plant and the lowest was observed in lemon grass plant (103/100g rhizosphere soil). The effects of AMF and microbial inoculation under labeled nitrogen fertilizer on root colonization of black cumin and anise plants after 30, 60 and 120 days of cultivation and the rhizosphere spore density at the end of the experiment have been studied. The maximum AMF root colonization in black cumin plant was 83.67% after 120 days in the composite AMF, Azotobacter chroococcum and Bacillus megatherium in the presence of half nitrogen ( 15 N) fertilizer dose, compared with the maximum AMF root colonization in anise plant that reached 76.67% after 120 days in the same treatment and the same nitrogen dose and this may be due to the difference between root exudates of two plants. The highest spore density in black cumin plant was 377/100g soil with the composite treatment in the presence of half nitrogen ( 15 N) fertilizer dose, while in anise plant it was 385/100g soil in the dual inoculation of AMF and Bacillus megatherium using half nitrogen dose.