the role of the substrate on germination of gigaspora albida schenck & smith was investigated. spores were desinfested with 0.5% sodium hypochlorite (20 min.) and placed on petri dishes over a millipore filter, with one of the following media: a- 1% water-agar; b- water-agar + aqueous extract of roots of panicum miliaceum l.; c- salt medium of murashige & skoog (ms) or sterilized sand; and incubated in the dark at room temperature (28oc ± 2). the experimental design was at random with four treatments and four replicates. germination was evaluated every 7 days until the 28th day. the water-agar medium was the most feasible for spore germination at the 7th day, followed by the ms medium at the 14th day. conversely, the sand and the root extract medium did not allow high germination. spores maintained in water-agar also presented longer germ tubes than spores in the other treatments. auxiliary cells were observed at the beginning of formation of hyphal branching in all treatments, however they were more numerous in the water-agar medium.