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This greenhouse study aimed to analyze the impact of arbuscular mycorrhizal (AM) fungal associations on maize (Zea mays L. hybrid Pioneer 3905) in order to compare their functional compatibility and efficiency. The AM fungus species used for this study were Glomus aggregatum, G. etunicatum, G. mosseae, and G. versiforme. Shoot and leaf masses, chlorophyll, soluble protein, total and reducing sugar, carbon (C), and nitrogen (N) concentrations, and glutamine synthetase (GS) activity in the maize leaves were analyzed. The root colonization ranged from 26% to 72% depending on the AM fungus species. Leaf mass was significantly higher when maize plants were colonized with G. etunicatum in comparison to the non-AM control. The mycorrhizal effect on dry leaf mass ranged from 15.9% to 23.9% depending on the AM species. However, the total shoot mass did not differ significantly among the treatments. The mycorrhizal treatment had a marginally significant effect on the chlorophyll concentrations in maize leaves. The protein concentration was the highest in the plants colonized with G. etunicatum and the N percentage was significantly higher in the leaves of plants colonized by G. versiforme or G. aggregatum than those with G. mosseae. However, the AM colonization did not significantly alter the GS activity among the treatments. The highest sugar concentrations were detected in the leaves of plants colonized by G. versiforme. The sugar concentrations as well as the C percentage were lower in the leaves of plants colonized by G. etunicatum compared to the other mycorrhizal treatments but the values were comparable to the non-AM control. Our overall results suggest that the expression of the mycorrhizal potential in the maize host plants varies among AM fungal species.

The sterol composition of spores from 16 species of arbuscular mycorrhizal fungi belonging to the order Glomales were examined by GC-MS. The major compound was found to be 24-ethylcholesterol (up to 85%) followed by cholesterol (up to 15%). Several other sterols such as 24-methylcholesterol, Δ5-avenasterol and 24-ethylcholesta-5,22-dien-3 β -ol were also detected. Significant amounts of α -amyrin, a common vascular plant triterpene, were present in the spores of all the fungal species analyzed. The absence of ergosterol, a classical fungal sterol, is discussed in relation to fungal evolution.