Interactions between Three Alfalfa Nodulation Genotypes and Two Glomus Species

Seedlings of a non-nodulating alfalfa (Medicago sativa L.) genotype (nod-fix-) and an ineffectively nodulating alfalfa genotype (nod+fix-) exhibited resistance to vesiscular-arbuscular mycorrhizal (VA mycorrhizal) colonization, when grown in pot cultures inoculated with either Glomus versiforme (Daniels and Trappe) Berch or Glomus intraradices Schenck and Smith. Appressoria, showing considerable variation in size and shape, developed on the root surface, but failed to form any internal structures such as arbuscules and vesicles. Wild-type (nod+fix+) alfalfa seedlings developed normal colonization. This phenomenon will be extremely useful in studying the processes of recognition and compatibility between plant species and VA mycorrhizal fungal species.