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Some Factors Affecting the Nodulation and Nodule Efficiency in Soybeans Infected by Soybean Mosaic Virus. J. C. Tu, Former 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(2), and C. R. Grau(3). (2)(3)Professor, and Undergraduate Assistant (now Graduate Research Assistant), respectively, Department of Botany and Plant Pathology, Iowa State University, Ames 50010. Phytopathology 60:1653-1656. Accepted for publication 15 June 1970. DOI: 10.1094/Phyto-60-1653.

Total nitrogen in nodules of soybeans infected by soybean mosaic virus (SMV) was consistently higher, and nodule weight was consistently lower, than in comparable healthy plants at different temperatures, daylengths, and growth stages. Differences in nodule weight between SMV-infected and healthy soybeans were small at 15.5 C, but increased with increasing temperature (to 26.5 C). Similarly, differences in nodule weight between SMV-infected and healthy soybeans were small at a short (6 hr) daylength, but increased at longer daylengths (10 and 14 hr). When inoculated with Rhizobium japonicum at different growth stages, healthy soybeans were always more susceptible to Rhizobium infection than were SMV-infected plants. Reduced susceptibility to R. japonicum, decreased leghemoglobin, and increased total nitrogen in SMV-infected soybean nodules suggests that nodules on SMV-infected plants were less efficient than nodules on healthy plants.