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Variations in yield components and grain yield of arbuscular mycorrhizal fungi (AMF) inoculated soybean varieties (Glycine max L. Merrill) grown in CO 2 enriched environment in the humid rainforest were tested. A screen house trial was established with soybean varieties ('TGx 1448-2E', 'TGx 1440-1E' and 'TGx 1740-2F'), AMF inoculation (with and without) and CO 2 enrichment (350±50 ppm and 550±50 ppm) in open top chamber, arranged in completely randomised design, replicated three times. A field trial was also conducted; the treatments were arranged in a split-split plot configuration fitted into randomised complete block design. In the main plot the variant was CO 2 enrichment, the sub-plot consisted of AMF inoculation (with and without), while the sub-sub plot consisted of soybean varieties, replicated three times. Both trials had significantly higher grain yield at elevated CO 2 than ambient. This could be attributed to improved yield attributes, more spore count and root colonisation. In both trials, inoculated soybean had significantly higher dry pod weight than un-inoculated, which could suggest the increased grain yield observed on the field. AMF inoculated soybean varieties outperformed uninoculated in both CO 2 enriched and ambient concentrations. AMF inoculated soybean variety 'TGx 1740-2F' is most preferable in CO 2 enriched environment, while variety 'TGx 1448-2E' had the most stable grain yield in all growth environments.

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Licensed under a Creative Commons Attribution 4.0 International License A field survey was conducted to assess root colonization, spore densities and relative abundance of native arbuscular mycorrhizal fungi (AMF) based on morphological aspects. Roots and rhizosphere soil samples were collected from established fields of selected oil seed crops [soybean (Glycine max L.), sesame (Sesamum indicum) and sunflower (Helianthus annuus)] and maize (Zea mays L.) grown in derived savannah agro-ecology of Southwest Nigeria. The mean percentage of AMF colonization across all crops was 60.8%, ranging from 34% to 87.5%, with highest root colonization observed in soybean. The spore densities retrieved from the different rhizospheres were relatively high, varying from 124 to 298 spores per 50 g dry soil, with highest spore densities observed in maize rhizosphere soils. The spore densities in the soil significantly correlated (r = 0.52, and P <0.05) with the root colonization. A total of 4 morphologically classifiable genera (Glomus, Gigaspora, Acaulospora, and Scutellospora) of AMF within the phylum Glomeromycota were detected. The dominant genus was Glomus in all the crops with highest relative abundance of 60.9%, followed by Acaulospora (21.3%) and Scutellospora (12.8%), with lowest relative abundance of AM spores observed for Gigaspora (5%). This study could contribute significantly to a better understanding of AMF community structure in derived savannah agro-ecology of Nigeria.