Viability and infectivity of mycorrhizal spores after long term storage in soils with different water potentials

Spores of three Glomus species were examined to compare the effect of long term storage under three different soil water conditions ( -0.04 MPa, -0 .8 MPa or dried) on their infective capacity. After 6 months of incubation, the infectivity tests showed that spores were affected in their potential as inoculum by soil water potential during storage. Spores from G. mosseae and G. deserticola were more infective after storage under 0.04 MPa soil water potential, while in G.fasciculatum the highest infectivity was obtained at -0 .8 MPa soil water potential. These results can not be ascribed to drought adaptation by the fungi during their production, since all spores used for this study were obtained from lettuce plants grown under the same conditions. The results appear to be related to the genetically determined ability of each fungus to tolerate drought. When the substrate was completely dried, the infective capacity of spores from the three fungi decreased considerably.