The viability and life cycle of spores of Glomus mosseae, a vesicular-arbuscular mycorrhizal fungus

• Main Author: Meier, Rose Antonia Zbinden
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-1992
• Subjects: Botany
• ISBN: 9798207915210

The viability and life cycle of spores of Glomus mosseae, a vesicular-arbuscular (VA) mycorrhizal fungus, was characterized. Isolates from three different sources were studied. Viability of VA mycorrhizal spores as determined by the vital stain tetrazolium bromide, or MTT, was compared with other methods; the bioassay and germination on agar. MTT staining was compared using the An and Hendrix (AH) versus Miller and Miller (MM) incubation protocols, autoclaving versus ethanol fixation, and fresh versus stored spores. With fresh nonperidiate spores MTT results underestimated viability as assessed by bioassay and germination. With stored nonperidiate spores the MM method overestimated viability from both bioassay and germination and the AH method correlated with only the bioassay. The outermost wall of the spore, the peridium, of the Kansas isolate develops in five stages: branch origination, weft formation, adherence of hyphae to spore wall, separation of the evanescent spore wall layer, and sloughing of the peridium. Peridial hyphae are present in two morphologically distinct layers. Fine radial canals were seen in both spore wall and, for the first time, in the peridium. Germination of freshly isolated nonperidiate spores of G. mosseae germinate via regrowth through the hyphal attachment and was accomplished by adding a comminution step before isolation of spores from the soil, and by using a sterilized coverslip culture with Hoagland's agar (no phosphorus). Germinated spores, hyphae, and secondary spores examined ultrastructurally revealed that all three structures were multinucleate, contained bacterium-like organelles (BLOs), lipids, mitochondria and vacuoles. Hyphae had occasional imperforate septa. Non host-associated intrahyphal hyphae and direct, through-the-wall germination observed in corn-associated silica sand culture, were reported for the first time. Lythrum salicaria, an emergent aquatic angiosperm, was found to be mycorrhizal in a St. Paul area wetland, but was not colonized by terrestrial VA mycorrhizal spore source, a nonperidiate isolate of G. mosseae, when grown in various P concentrations (0 to 10,000 $\mu$g/l) in the growth chamber.