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Soilborne Pathogens on Cereals in a Highland Location of Mexico. D. A. Lawn, Centro Internacional de Mejoramiento de Maiz y Trigo (CIMMYT), Lisboa 27, Apdo. Postal 6-641, Col. Juarez, Deleg. Cuauhtemoc, 06600 Mexico D.F., Mexico. K. D. Sayre, Centro Internacional de Mejoramiento de Maiz y Trigo (CIMMYT), Lisboa 27, Apdo. Postal 6-641, Col. Juarez, Deleg. Cuauhtemoc, 06600 Mexico D.F., Mexico. Plant Dis. 76:149-154. Accepted for publication 11 August 1991. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-0149.

Fumigation trials with methyl bromide and dazomet were established in El Batan, Mexico, during 1988 and 1989. Genotypes of triticale ( Triticosecale), bread wheat (Triticum aestivum), and durum wheat (Triticum durum) were evaluated for susceptibility to indigenous soilborne pathogens. The predominant pathogens identified included Cochliobolus sativus, Fusarium spp., Gaeumannomyces graminis var. tritici, and Pratylenchus thornei. Initial infections on all genotypes were predominantly attributable to C. sativus, but when present, G. g. tritici was the predominant pathogen on the bread wheat and durum wheat genotypes by a milk stage of development. In 1989, G. g. tritici was isolated from 10% of the discolored triticale roots sampled at this stage, compared with 60 and 63% from the discolored bread wheat and durum wheat roots, respectively. Analysis of variance indicated significant fumigation effects on soil populations of P. thornei at planting and harvest. Significantly greater reproduction of P. thornei occurred on the bread wheat genotypes than on either durum wheat or triticale. Higher tiller numbers were observed throughout the season in both years after fumigation. Fumigation significantly increased the number of spikes per square meter but not vegetative biomass. Because of severe weather, yield data provided no clear indications of the degree of pathogenicity posed by soilborne pathogens.