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Enzyme-Linked Immunosorbent Assay Quantification of Initial Infection of Wheat by Gaeumannomyces graminis var. tritici as Moderated by Biocontrol Agents. H. M. El-Nashaar, Postdoctorate research associate, Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331, Present address of senior author: USDA, ARS, Plant Science Research Laboratory, P.O. Box 1029, Stillwater, OK 74076; L. W. Moore(2), and R. A. George(3). (2)(3)Associate professor, and research assistant, respectively, Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331. Phytopathology 76:1319-1322. Accepted for publication 29 May 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/Phyto-76-1319.

An ELISA-double antibody sandwich system was used to measure the quantity of Gaeumannomyces graminis var. tritici associated with roots of winter wheat. The seedlings were grown at 15 2 C in sand infested with three concentrations of 1-mm particles of oat grains colonized by G. g. var. tritici. Six days after seeding the pathogen was readily detected in a homogenized suspension (10-7 dilution) of roots that were exposed to the lowest concentration. The level of G. g. var. tritici in the roots was proportional to the amount of inoculum used (r = 0.998). When wheat seeds were coated with strains of antagonistic bacteria before sowing, the amount of G. g. var. tritici detected in the roots was as much as 79% lower than in the absence of the bacteria. The results indicate that the amount of G. g. var. tritici associated with wheat roots can be measured within 6 days from seeding, and that in this system, potential antagonists to G. g. var. tritici can be evaluated within 8-10 days from planting.

Additional keywords: biological control, monoclonal antibodies, soilborne plant pathogens, take-all, wheat.