Detection of the arbuscular mycorrhizal fungus Scutellospora heterogama within roots using polyclonal antisera

The antigenic properties of the arbuscular mycorrhizal Scutellospora heterogama (BEG 35) were studied to develop a serological method for detecting the fungus in roots. Three polyclonal antisera were raised against the combined soluble and particulate fraction of spores of S. heterogama (BEG 35) and used in serological tests. When the soluble fraction of crushed spores was used as antigens in Ouchterlony double diffusion tests, all these antisera showed a high degree of specificity for the homologous fungus. No cross-reactivity was found with Glomus geosporum, Acaulospora spp., Entrophospora colombiana, Gigaspora spp. or other Scutellospora spp. Immunostaining of Western blots using one of the antisera was less specific but major cross-reactions were limited to fungi in Scutellospora, which all produced different banding patterns. This enabled immunostaining of Western blots to be used to detect and discriminate S. heterogama (BEG 35) and a morphologically similar Scutellospora sp. (BEG 40) in plant roots. There was no cross-reaction with uncolonized roots. All bands detected in extracts from colonized roots corresponded to bands detected in spore extracts, but some additional bands were unique to the spores. No significant reaction was observed with roots colonized by arbuscular mycorrhizal fungi outside the genus Scutellospora. The antiserum may thus be used to track species of Scutellospora within plant roots.