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Disease Detection and Losses

Quality Losses in Phomopsis-Infected Soybean Seeds. P. R. Hepperly, Graduate research assistant, Department of Plant Pathology, University of Illinois, Urbana, IL 61801; J. B. Sinclair, professor, Department of Plant Pathology, University of Illinois, Urbana, IL 61801. Phytopathology 68:1684-1687. Accepted for publication 24 July 1978. Copyright © 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-1684.

Several measurements of seed quality were used to compare soybean (Glycine max ‘Wells’) seeds with and without symptoms or signs of Phomopsis sojae infection. Seeds with symptoms contained more oil, protein, and recoverable P. sojae than symptomless seed. In addition, symptomatic seeds were smaller in size and volume, were lower in density, produced lower quality oil and flour, and had lower viability and durability than did symptomless seeds. Quality losses in symptomatic seeds were associated with premature death and the breakdown of seedcoat tissues. Thiram seed treatment reduced recovery of P. sojae from both symptomless and symptomatic seeds on PDA, but more effectively controlled the fungus in symptomless seeds than in symptomatic seeds. Seed quality losses attributed to “weathering” were due in part to P. sojae infection.

Additional keywords: Pod and stem blight.