Vesicular-arbuscular mycorrhiza-an evolutionary approach

Abstract

Vesicular arbuscular mycorrhizal (VAM) fungi forming mutuanstic symbiosis with roots of higher plants are present in soil throughout the world. This suggests that VAM fungi disseminated intercontinentally prior to continental drift of the supercontinent Gondwana. The first mycorrhizal symbiosis appears to have occurred early in geological time, as evidenced by their presence in fossil soil and roots. Evidences available to date suggest that VAM fungi co-evolved with land plants. The ability of the host and fungus to maintain the association depend on favourable gene combinations in both partners. Differences in morphology and development of spores of different VAM fungi reflect independent evolution from a number of distinct points of origin. The centre of evolution of VAM fungi appears to be the tropics.