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Frequency and Pathogenicity of Fusarium solani Recovered from Soybeans with Sudden Death Syndrome. J. C. Rupe, Department of Plant Pathology, University of Arkansas, Fayetteville 72701. . Plant Dis. 73:581-584. Accepted for publication 3 January 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0581.

A blue isolate of Fusarium solani was obtained from roots and lower stems of soybeans with sudden death syndrome (SDS) grown in 10 fields in Arkansas, one field in Illinois, and one field in Kentucky. The blue F. solani was recovered from plants from all locations and from 86% of all plants sampled. Nineteen percent of isolates from lateral root sections, 23% of isolates from taproot epidermal sections, 12% of isolates from taproot cortical sections, and 6% of isolates from lower stem sections assayed yielded the fungus. One representative isolate was used to inoculate the taproots of flowering 6-wk-old, greenhouse-grown soybeans (cv. Lee 74). Of the 149 plants inoculated, 76.5% developed foliar symptoms similar to SDS. Recovery of the blue F. solani from inoculated plants completed Koch’s postulates. Eleven single-spore isolates from nine locations were used to inoculate 2-wk-old Lee 74 soybean plants by placing a plug of mycelium next to the stem immediately below the soil line. Disease development was similar to that in older plants. Ten isolates produced symptoms similar to SDS, but the symptoms varied greatly in intensity. These results strongly suggest that a specific type of F. solani is involved in SDS.