Effect of Citrus Root Exudates on Germination of Chlamydospores of the Vesicular-Arbuscular Mycorrhizal Fungus, Glomus Epigaeum

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Abstract
The effect of root exudates from Troyer citrange (Poncirus trifoliata x Citrus sinensis) on germination of surface-sterilized chlamydospores of the vesicular-arbuscular mycorrhizal (VAM) fungus, Glomus epigaeum, was examined on water agar. Optimum temperature for spore germination was 25 C. After 7 da exposure of spores to root exudates, germination was increased from less than 10% (distilled water control) to up to 27%. Germ tube length of exudate-treated spores was more than four times greater than that of untreated spores. Root exudates stimulated branching of germ tubes, whereas germ tubes of untreated spores branched infrequently. These results indicate that root exudates affect spore germination and germ tube growth of G. epigaeum and thereby could influence subsequent root colonization and VAM formation.