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Free Amino Acids in Soybeans Infected with Soybean Mosaic Virus, Bean Pod Mottle Virus, or Both. J. C. Tu, Postdoctoral Research Associate, Department of Botany and Plant Pathology, Iowa State University, Ames 50010, Present address of senior author: Department of Plant Science, University of Alberta, Edmonton, Alberta, Canada; R. E. Ford, Professor, Department of Botany and Plant Pathology, Iowa State University, Ames 50010. Phytopathology 60:660-664. Accepted for publication 4 November 1969. DOI: 10.1094/Phyto-60-660.

Free amino acids were measured quantitatively in soybean (Glycine max) leaves infected with three soybean mosaic virus (SMV) isolates differing in virulence and with bean pod mottle virus (BPMV) alone or in combination with SMV. Total free amino acids and ammonia increased with virus infection. Individual amino acids decreased, however, or were variable depending on the SMV isolate. Free amino acid content appeared closely correlated with symptom severity. Free amino acid concentration increases were in order of SMV-O- > SMV-NC- > SMV-M-infected soybean. BPMV and SMV-O had a synergistic effect on soybeans in some free amino acids, because free amino acid increased in mixed infections but did not increase in proportion with increased disease severity.