Onion (Allium cepa) and Barley (Hordeum vulgare) colonized by Glomus mosseae, G. fasiculatum, and G. intraradices were grown in aeroponic cultures. After 14 weeks, all roots were colonized by the inoculated vesicular-arbuscular mycorrhizal fungi. Abundant vesicles and arbuscules formed in the roots, and profuse sporulation was detected intra- and extra-radically. Within each fungal species, barley contained significantly more roots and spores per plant than onion did, although the percent root colonization was similar for both hosts. Mean percent root colonization and sporulation per centimetre of colonized root generally increased with time, although with some treatments colonization declined by week 14. Spore production ranged from 4 spores per cm of colonized root for G. fasiculatum to 51 spores per cm for G. intraradices. Infectivity trials with root inocula resulted in a mean ranged from 28.9 to 51.1% of onion roots colonized by
G. mosseae, G. fasiculatum, and G. intraradices, respectively, while in aeroponic culture it ranged from 33.8 to 38. However, infectivity studies comparing G. fasiculatum spores from soil and aeroponic culture indicated no biological differences between the spore sources. Aeroponically produced G. mosseae and G. fasiculatum inocula retained their infectivity after cold storage (4°C) in either sterile water or moist vermiculite for at least 4 and 9 months, respectively.