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Tobacco Streak Virus Isolated from Soybeans, Glycine max. Helen Herron Fagbenle, Research Assistant, Department of Botany and Plant Pathology, Iowa State University, Ames 50010, Present address of senior author: Department of Plant Pathology, University of Illinois, Urbana 61801; Richard E. Ford, Professor, Department of Botany and Plant Pathology, Iowa State University, Ames 50010. Phytopathology 60:814-820. Accepted for publication 7 December 1969. DOI: 10.1094/Phyto-60-814.

Tobacco streak virus (TSV) was isolated from naturally infected soybeans (Glycine max) for the first time in Iowa and in the USA. This TSV isolate had a thermal inactivation point of 58 C, dilution end point of 1:640, longevity in vitro of 24 hr, and a host range similar to a Brazilian strain of TSV isolated from soybean. It was inactivated more rapidly in tobacco sap than in cowpea or bean sap. At the end of 30 min, a 1:25 dilution of tobacco leaf sap infected with TSV was more infective than dilutions of 1:1 or 1:10. TSV infection in soybeans reduced seed and pod production and embryo vigor. Infective virus particles were 28 to 32 mµ in diam. The Iowa TSV isolate reacted only with TSV antiserum. Cassia occidentalis is a new host for TSV.