New Physiological Race of Peronospora manshurica Virulent to the Gene Rpm in Soybeans. S. M. Lim, USDA-ARS, Professor, Department of Plant Pathology, University of Illinois at Urbana-Champaign, Urbana 61801. R. L. Bernard, USDA-ARS, Professor, Department of Agronomy, C. D. Nickell, Associate Professor, Department of Agronomy, and L. E. Gray, USDA-ARS, Associate Professor, Department of Plant Pathology, University of Illinois at Urbana-Champaign, Urbana 61801. Plant Dis. 68:71-72. Accepted for publication 29 August 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, 1984. DOI: 10.1094/PD-68-71.

In 1981, a new race of Peronospora manshurica virulent on the soybean (Glycine max) cultivar Union, which carries the gene Rpm for downy mildew resistance to all previously known races, occurred in the Illinois soybean disease monitoring plots. The reaction of 18 soybean cultivars was determined to the new race, designated race 33, as well as to race 2, which was collected at Urbana from the cultivar Williams before downy mildew appeared on Union. Five cultivars (Pridesoy, Palmetto, Kabott, Ogden, Acadian) from a set of differential cultivars and three others (Fayette, Tracy, PI 88788) were found to be resistant to both race 2 and race 33.