First Report of Race 1 of Phytophthora megasperma f. sp. glycinea on Soybean in Delaware. C. A. Thomas, USDA-ARS, Plant Pathology Laboratory, Beltsville, MD 20705. P. R. Thomison, Department of Agronomy, University of Maryland, College Park 20742. Plant Dis. 70:78. Accepted for publication 2 October 1985. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-78f.
The incitant of a root and stem rot of Glycine max (L.) Merr. ‘Verde’ in a planting near Georgetown, Delaware, in 1984 was found to be race 1 of Phytophthora megasperma Drechs. f. sp. glycinea Kuan & Erwin. Identification was based on the morphological and cultural characteristics of the pathogen, on comparison to isolates of race 1 from Illinois and Maryland, and on reactions to hypocotyl inoculation of six differential host cultivars (the susceptible Harosoy and the resistant Sanga, Harosoy 63, Mack, Altona, and PI 103091) and the resistant cultivar Tracy. Of five soybean cultivars widely grown in Delaware, Essex and Williams were shown to be susceptible and Union, Williams 82, and Pella to be resistant.