Morphology of arbuscular mycorrhizas is influenced by fungal identity

There are two main morphological types of arbuscular mycorrhizas (AM), the Arum-type and the Paris-type. It is often accepted that AAA morphology is c ontrolled by plant identity. In this experiment the influence of fungal identity on the morphology of AM was investigated. Wild-type (76R) tomato (Lycopersicon esculentum) was gro wn in association with six different AM fungal species in nurse pots. The m orphology of the AM was assessed quantitatively using the magnified interse cts technique. Three of the fungal species (Glomus intraradices, G. mosseae, G. versiforme ) formed the Arum-type, with characteristic intercellular hyphae and arbusc ules. The remaining three species (Gigaspora margarita, Glomus coronatum, a nd Scutellospora calospora) formed the Paris-type, with hyphal and arbuscul ate coils. The results demonstrate that the morphology of AM is not solely under plant control but is also influenced by fungal identity. Possible reasons for th e differences observed and the functional implications are discussed.