Comparison of Two Methods for Quantifying Extraradical Mycelium of Vesicular‐Arbuscular Mycorrhizal Fungi

Abstract Extraradical mycelium of Glomus mosseae (Nicol. & Gerd) Gerd. and Trappe, a vesicular‐arbuscular mycorrhizal (VAM) fungus, was assessed by two quantitative methods using subsamples of the same soil. Fungal biomass was determined by a chitin assay and the length of fungal hyphae in the soil was obtained by direct microscopic measurements. Total hyphal length, including hyphae <5 µm in diameter, was not correlated ( P > 0.05) with total soil chitin; however, the length of hyphae ≥ 5µm in diameter correlated significantly ( P < 0.01) with VAM‐fungal biomass. There is a strong relationship between these methods for the determination of the extraradical VAM‐fungal mycelium. The two methods permit the calculation of a “specific mass' (µg/m) for VAM‐fungal hyphae. Considerations for using either method to quantify extraradical VAM‐fungal mycelium are discussed.