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Elevated pH and Associated Reduced Trace-Nutrient Availability as Factors Contributing to Take-All of Wheat upon Soil Liming. E. M. Reis, Plant pathologist, Centro Nacional de Pesquisa de Trigo, Caixa Postal, 569, 99.100 Passo Fundo, RS, Brazil; R. J. Cook(2), and B. L. McNeal(3). (2)Research plant pathologist, Agricultural Research Service, U.S. Department of Agriculture, Pullman, WA 99164; (3)Professor, Department of Agronomy and Soils, Washington State University, Pullman 99164. Phytopathology 73:411-413. Accepted for publication 8 September 1982. 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, 1983. DOI: 10.1094/Phyto-73-411.

Studies of take-all of wheat caused by Gaeumannomyces graminis var. tritici tested whether increased severity of the disease in areas where soil had been amended with limestone was the result of increased pH of the rooting medium or of calcium or magnesium supplied by the amendments. Hoagland's solution was used as a source of plant nutrients and was applied to a silica sand rooting medium with calcium or magnesium at normal (1H), twice (2H), or three times (3H) the amount in Hoagland's solution, each at pH 4.5, 5.5, 6.5, 7.5, and 8.5. Take-all severity increased with increasing pH but not with increasing amount of calcium or magnesium. Increasing calcium from 1H to 3H had no effect on take-all, but increasing magnesium from 2H to 3H resulted in less severe take-all. Uptake of copper, magnesium, and iron (as determined by leaf-tissue analysis of plants supplied with normal [1H] Hoagland's solution) was significantly less at pH 7.5 and 8.5 than at the three lower pH levels; for zinc, uptake was significantly less at pH 5.5 and above than at pH 4.5. The pH values associated with reduced uptake of trace nutrients corresponded generally to the pH values at which the incidence and severity of take-all was increased. At least part of the favorable effect of liming on take-all may result from host-plant predisposition resulting from inadequate supplies of certain essential plant nutrients at the elevated pH.

Additional keywords: soilborne pathogens, Triticum aestivum.