Colonization of wheat roots by Gaeumannomyces graminis inhibited by specific soils,microorganisms and ammonium-nitrogen |
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Authors: | Richard W Smiley |
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Institution: | Department of Plant Pathology, Cornell University, Ithaca, N.Y. 14853, U.S.A. |
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Abstract: | Lineal extension of Gaeumannomyces graminis var. tritici hyphae along roots of intact wheat plants growing in soils was measured. Hyphal growth rates were lower in soils treated with NH4+-N than with NO3?-N. In a soil that is suppressive to the take-all disease, the controlling influence of NH4+-N was eliminated by soil fumigation (methyl bromide), and reintroduced to fumigated soil by additions of 1% nonsterile soil. Effects of fumigation on hyphal growth were absent in a nonsuppressive soil, and in NO3?-treatments of the suppressive soil. When inocula of selected groups of wheat rhizoplane microflora were reintroduced into a fumigated or a soil-reinoculated soil via a root-food base, the Pseudomonas spp. consistently appeared more suppressive in NH4+-N treatments than the general bacterial flora, Bacillus spp. spores, streptomycetes, and fungi. |
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