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Phosphorus amendment inhibits hyphal branching of the AM
fungus Gigaspora margarita directly and indirectly through
its effect on root exudation
poster
DOUDS, DAVID, JERRY Nagahashi, and GLORIA Abney
USDA-ARS ERRC, 600 E. Mermaid Lane, Wyndmoor, PA 19038-8038
USA
ICOM1 Abstract
The direct or indirect nature of the inhibition of
mycorrhizal development by phosphorus is still debated, but
the exact effect upon the mycorrhizal fungus in the soil is
not understood. To this end, the effect of solution P
concentration upon growth of pregerminated spores of the
arbuscular mycorrhizal fungus Gigaspora margarita was
examined in vitro. One mM P significantly inhibited
branching of the primary germ tube. The number of branches
and the total hyphal length were both significantly inhibited
at 10 mM P. In addition, germinated spores exposed to
exudates produced by Ri T-DNA transformed roots of Daucus
carota grown in the presence of P showed significantly less
hyphal branching than those exposed to exudates produced by P
stressed roots. These phenomena could contribute to the
observed inhibition of mycorrhiza formation by high P.