Variation in propagule numbers of vesicular-arbuscular mycorrhizal fungi in a semi-arid soil

Abstract

Measured by the MPN method, low densities of propagules of vesicular-arbuscular mycorrhizal fungi were found in a soil from a semi-arid site in South Australia. The only spores that germinated within 7 days were found more than 10 cm down the soil profile. The proportion of germinated spores of Scutellospora calospora was greater than the measured density of propagules, suggesting that the MPN method underestimates the number of propagules. Spores are unlikely to be important for the initiation of vesicular-arbuscular mycorrhizas at the site, since pre-germinated seedlings transplanted to moistened soil became mycorrhizal within 6 days. The only spores found below 30 cm in the profile did not survive when exposed to the wet/dry cycles which occur at the soil surface over summer. The results suggest that different species of vesicular-arbuscular mycorrhizal fungi have different survival strategies for existence at the study site.