VIEW ARTICLE

Ecology and Epidemiology

Rhizoctonia-Rhizobium Interactions in Relation to Yield Parameters of Soybean. R. G. Orellana, Research Plant Pathologist, Applied Plant Pathology Laboratory, U.S. Department of Agriculture, Beltsville, Maryland 20705; C. Sloger(2), and V. L. Miller(3). (2)Research Plant Physiologist and Agronomist, Plant Nutrition Laboratory, U.S. Department of Agriculture, Beltsville, Maryland 20705; (3)Chief, Farm Management Branch, Division of Operations, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, Maryland 20705. Phytopathology 66:464-467. Accepted for publication 3 October 1975. DOI: 10.1094/Phyto-66-464.

Rhizoctonia solani significantly reduced top and nodule weights of Lee and Kent soybeans inoculated with Rhizobium japonicum and grown in a N-free sand-nutrient substrate as compared with plants grown with Rhizobium alone. For Lee soybeans, a 63% decrease in fixed N per plant due to the fungus was demonstrated. In Rhizobium-inoculated Kent soybeans grown in the presence of Rhizoctonia at either 15, 20, or 25 C, top and nodule weights and the total N content per plant were also reduced. Because resistance in soybeans to Rhizoctonia root rot is not presently available and the direct effects of this fungus on R. japonicum are unknown, this fungal pathogen may be a yield-limiting factor under a wide range of ecological conditions.