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Occurrence and Transfer of a Biological Factor in Soil that Suppresses Take-all of Wheat in Eastern Washington. P. J. Shipton, Plant Pathologist, Mycology Division, The North of Scotland College of Agriculture, Aberdeen AB9 1UD; R. J. Cook(2), and J. W. Sitton(3). (2)(3)Research Plant Pathologist, and Agricultural Research Technician, Agricultural Research Service, U.S. Department of Agriculture, Pullman, Washington 99163. Phytopathology 63:511-517. Accepted for publication 24 October 1972. DOI: 10.1094/Phyto-63-511.

A biological factor antagonistic to Ophiobolus graminis (=Gaeumannomyces graminis) occurs in eastern Washington fields of long-term dryland or irrigated wheat culture, but is absent from or present in ineffective amounts in noncultivated grassland and virgin soils. Severe take-all has been observed primarily in commercial fields of the Columbia Basin recently converted from their virgin state (native bunchgrass and sagebrush vegetation) to intensive wheat production with irrigation, but not in wheat fields with a long history of irrigated or dryland wheat. The fungus is prevalent in all soils, but apparently is suppressed in some by microbial antagonism. The antagonistic properties of a soil were eliminated in the field and greenhouse by methyl bromide fumigation, and in the greenhouse by steam-air pasteurization at 60 C. As little as 1% addition of antagonistic soil to fumigated soil provided excellent restoration of antagonistic properties to the fumigated soil, and some restoration of antagonism in soil in field plots. In contrast, amendment of fumigated soil with virgin soil at 1 and 10% w/w provided little or no restoration of antagonism. This demonstrated the difference in antagonism between cropped and virgin soils, and the transmissibility of the factor in the greenhouse and the field. The nature of the antagonistic factor is discussed.

Additional keywords: biological control, soil microbiota.