DE SOUZA, FRANCISCO ADRIANO1 & RICARDO LUIS LOURO BERBARA2.
1 Embrapa-Agrobiologia, km 47 antiga rodovia Rio-São Paulo, Seropédica, Caixa Postal 74505, CEP 23851-970, Rio de Janeiro, Brazil. 2 Departamento de Solos, Universidade Federal Rural do Rio de Janeiro, km 47 Antiga Rodovia Rio-São Paulo, Seropédica, CEP 23851-970, Rio de Janeiro, Brasil.
The sporeontogeny of Glomus clarum was monitored in transformed roots of clover (Trifolium repens) and carrot (Daucus carota). After spore germination in water agar it starts to produce spore-like vesicles during the non symbiotic phase. It has been shown that these structures were in fact juvenile spores that after root colonisation, developed into mature spores. Thus, G. clarum was shown to be able to trigger the spore formation at the nonsymbiotic phase. However, without an effective symbiotic establishment the juvenile spores structures will senesce. Spores of the genus Glomus are assumed to form terminally from sporogenic hyphae, but the ontogeny of G. clarum demonstrates that sporogenesis occurs from intercalar spore-like vesicle structures formed along the sporogenic hyphae. The spore ontogeny pattern represents a morphologically distinct group that diverges from the description given to for genus Glomus but resembles the Acaulosporacea spore ontogeny. In culture systems with transformed roots all steps of spore formation can be followed greatly contributing to a better understanding of events that occur during the pre- and post-colonization phase possibly filling some gaps in the taxonomy of these fungi and hence contributing to the study of the phylogenetic relationships among taxonomic units study of this symbiont.