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Interactions of Vesicular-Arbuscular Mycorrhizal Fungi, Root-Knot Nematode, and Phosphorus Fertilization on Soybean. D. E. Carling, Agricultural and Forestry Experiment Station, University of Alaska, Palmer 99645. R. W. Roncadori, and R. S. Hussey. Department of Plant Pathology, University of Georgia, Athens 30602. Plant Dis. 73:730-733. Accepted for publication 16 March 1989. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1989. DOI: 10.1094/PD-73-0730.

The effects of two vesicular-arbuscular mycorrhizal (VAM) fungi, Meloidogyne incognita, and phosphorus (P) fertilization (0, 25, 50, and 150 ?g/g of soil) on soybean growth and yield were determined in a greenhouse study. Maximum growth and yield occurred at P fertilization rates of 50150 ?g/g, regardless of whether plants were uninoculated or were inoculated with Gigaspora margarita, Glomus etunicatum, or M. incognita or coinoculated with either endophyte and the nematode. Growth and yield were stimulated by mycorrhizae at the lowest P rate. The performance of non-VAM and VAM plants was little affected by M. incognita at any P rate; therefore, tolerance to the nematode could not be evaluated. Egg production on VAM plants (eggs per root system and eggs per gram of root) was suppressed at the lowest P rate as well as by increased P fertilization, indicating the induced resistance is possibly due to improved P nutrition in the host. M. incognita had no effect on root colonization by VAM fungi, but at the lowest P rates, the nematode stimulated sporulation by G. margarita and suppressed sporulation by G. etunicatum.

Keyword(s): endomycorrhizae.