Rapid and sensitive bioassay to study signals between root exudates and arbuscular mycorrhizal fungi

A sensitive bioassay was developed to provide a way to detect chemical sign als from host plants which induce changes in hyphal growth patterns of germ inated spores of arbuscular mycorrhizal (AM) fungi. The assay can be used t o test host root exudates, as well as particulate fractions (root cap borde r cells and root mucilage), for their ability to affect AM fungal growth. H yphal branching, induced by various host root components, can be detected a s early as 4 h although results of the bioassay were usually determined aft er 16 to 24 h. The type of branching pattern observed was dose-dependent.