VIEW ARTICLE

Brown Stem Rot Resistance and Its Modification by Soybean Mosaic Virus in Soybeans. H. Tachibana, Research Plant Pathologist, Plant Science Research Division, ARS, USDA, Department of Botany and Plant Pathology, Iowa State University, Ames 50010; L. C. Card, Agricultural Research Technician, Plant Science Research Division, ARS, USDA, Department of Botany and Plant Pathology, Iowa State University, Ames 50010. Phytopathology 62:1314-1317. Accepted for publication 24 May 1972. DOI: 10.1094/Phyto-62-1314.

Resistance to brown stem rot (BSR) of soybeans was confirmed by artificial inoculations in the greenhouse. One line, P.I. 86.150, had 30% less BSR than P.I. 84.946-2, current principal source of BSR resistance for breeding purposes. Occurrence of soybean mosaic virus (SMV) in BSR-resistant lines was observed. Relationship between seed coat mottling, a symptom of SMV, and BSR resistance was inverse. When plants from nonmottled and mottled seed of BSR susceptible Clark cultivar and resistant P.I. 84.946-2 were inoculated with Cephalosporium gregatum, plants from mottled seed had half as much disease as did plants from nonmottled seed. Individual and combination inoculations of SMV and C. gregatum in BSR-susceptible Ontario cultivar further indicated half as much BSR with both virus and fungus as with C. gregatum alone.