Colonization patterns in a mycorrhiza-defective mutant tomato vary with different arbuscular-mycorrhizal fungi

Interactions between a mycorrhiza-defective tomato (Lycopersicon esculentum) mutant, rmc, and different species of arbuscular mycorrhizal (AM) fungi were investigated and compared with those with the wild-type cv. 76R. Both cv. 76R and rmc were challenged with Glomus intraradices, G. mosseae, G. coronatum, G. versiforme, G. etunicatum, G. fasciculatum, Gigaspora margarita and Scutellospora calospora using a nurse pot inoculation system. Cv. 76R demonstrated normal colonization patterns for all fungal species. By contrast, the development of different fungal species with rmc was impaired at different steps. Development of G. intraradices, G. etunicatum and G. fasciculatum was arrested on the root surface. However, G. mosseae, G. coronatum, G. margarita and S. calospora frequently penetrated the root epidermis, but colonization of the cortex was rare. G. versiforme achieved relatively normal colonization in rmc compared with the other species. This is the first report on the variation of colonization patterns in a mycorrhiza-defective mutant by different species of AM fungi, and highlights the need for previously described mutants in legumes to be challenged by more than one fungus. © New Phytologist (2001)