Hyphae of a vesicular—arbuscular mycorrhizal fungus maintain infectivity in dry soil, except when the soil is disturbed

SUMMARY We examined the hypothesis that hyphae of a VA mycorrhizal fungus in dry soil remain infective, but that the infectivity decreases if the soil is disturbed. We used split‐pots, and sealed cylinders of nylon mesh, to create volumes of dry soil which contained hyphae of Acaulospora laevis Gerd. and Trappe that were attached, outside the mesh, to roots of living plants of Acacia satigna . (Labill.) H. Wendl. After the soil was dried in situ , the hyphae were detached from the roots without soil disturbance, or the soil containing the hyphae was disturbed. The infectivity of the hyphae after these treatments was then compared with that of intact hyphae. External hyphae of A. laevis remained highly infective in soil in which the matric potential had reached −21 MPa. Hyphae detached from the original host plant roots were equally infective. However, disturbance of the dry soil containing the external hyphae severely reduced the infectivity of the hyphae. After fluorescent staining, fungal structures with fluorescing nuclei were readily visible both within, and attached to, roots of A. Saligna which had no fluorescing nuclei.