Stimulation of Germination of Spores ofGlomus Versiformeby Spore-Associated Bacteria

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Abstract
Germination of spores of Glomus versiforme (Karsten) Berch (=Glomus epigaeum Daniels and Trappe) was greatly reduced by surface disinfestation to remove naturally associated microbial flora. Spores which remained contaminated with bacteria after surface disinfestation germinated at a much higher rate than did spores with no evident bacterial contamination. Germination of non-surface disinfested spores was minimal on Nobel agar, a medium which did not support visible growth of spore-associated bacteria. On Bacto agar, a medium which did support growth of spore-associated bacteria and fungi, spore germination was minimal when bacterial growth was inhibited by antibiotics, but was significantly greater when spore-associated bacterial growth was not inhibited by antibiotics. Germination of surface disinfested spores was increased 1.5- to 2.2-fold by addition of bacteria previously isolated in pure culture from non-surface disinfested spores. Hyphae emerging from spores in the presence of the bacteria were smooth, developed small vesicles, and were substantially longer and more extensively branched than those from surface disinfested spores without bacteria. The latter hyphae were characterized by meager growth, an abnormal knobbed appearance, and a lack of vesicle formation. Spore-associated bacteria capable of stimulating germination of spores of G. versiforme were found to belong to several different genera, including Pseudomonas and Corynebacterium.