In situ analysis of anastomosis in representative genera of arbuscular mycorrhizal fungi.

Arbuscular mycorrhizal fungi (AMF) form obligate symbiotic associations with plants. As a result, the role of hyphal interactions in the establishment and maintenance of common mycorrhizal networks is poorly understood because of constraints on methods for in situ analysis. We designed a rhizohyphatron that allows the examination of intact mycelia growing from whole mycorrhizal plants. Plants preinoculated with spores were cultivated in a compartment with a connecting tube from which hyphae extend through a fine nylon mesh onto agar-coated slides. Species selected from each of the five AMF genera were used to assess and characterize the anastomosis behavior in the rhizohyphatron. Hyphal networks of Paraglomus occultum, Ambispora leptoticha, Scutellospora heterogama, and Gigaspora gigantea growing on the agar-coated slides showed no evidence of hyphal fusion. In contrast, anastomosis occurred in the hyphal networks of Glomus clarum and Glomus intraradices at an average frequency of less than 15% for both species. The rhizohyphatron developed in this study will provide knowledge of the biology and genetics of self/non-self recognition in AMF and help to better understand Glomeromycotan life history strategies.