VIEW ARTICLE

Physiology and Biochemistry

Specific Effects of Soybean Mosaic Virus on Total N, Ureide-N, and Symbiotic N₂-Fixation Activity in Glycine max and G. soja. R. G. Orellana, Research plant pathologist, the Plant Pathology and the Nitrogen Fixation and Soybean Genetics Laboratories, ARS, S&E, U.S. Department of Agriculture, Beltsville, MD 20705; S. L. Reynolds(2), C. Sloger(3), and P. van Berkum(4). (2)(4)Research associates, Botany and Agronomy Departments, University of Maryland, College Park 20742; (3)Plant physiologist, the Plant Pathology and the Nitrogen Fixation and Soybean Genetics Laboratories, ARS, S&E, U.S. Department of Agriculture, Beltsville, MD 20705. Phytopathology 73:1156-1160. Accepted for publication 14 March 1983. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1983. DOI: 10.1094/Phyto-73-1156.

Plants of cultivated soybeans (Glycine max ‘Hill’ and ‘Essex’) and two introductions of wild annual soybean, G. soja PI 424-005 and PI 378-693-B, were studied in the greenhouse for their response to soybean mosaic virus. Significant decreases in top and nodule weights had occurred after 53 days in plants inoculated in the primary leaf stage with the Beltsville isolate of soybean mosaic virus (SMV-B). Plants of G. soja infected with SMV-B had significantly higher total N and ureide-N contents than the controls. Plants of G. max cultivar Hill showed no significant differences for these two parameters, while total N increased significantly in infected plants of cultivar Essex. N₂-fixation activity, measured by the acetylene reduction assay, decreased significantly in all genotypes except Hill. Measurements of nodule-specific nitrogenase activity indicated that nodules from plants infected with SMV-B of Hill and PI 378-693-B fixed N₂ at rates exceeding those of the uninoculated controls. The presence of SMV-B was detected by ELISA in inoculated plants at harvest. Leaves developed higher virus concentrations than did nodules, and there was no correlation between foliar virus titer and symptom severity ratings. Symptoms were most severe on G. soja PI 424-005, less severe on G. max cultivar Essex and G. soja PI 378-693-B, and least severe on G. max cultivar Hill.