Soybean Cultivar Reactions to Soybean Stem Canker Caused by Diaporthe phaseolorum var. caulivora and Pathogenic Variation Among Isolates. B. L. Keeling, Research Plant Pathologist, U.S. Department of Agriculture, Agricultural Research Service, Stoneville, MS 38776. Plant Dis. 69:132-133. Accepted for publication 20 July 1984. 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, 1985. DOI: 10.1094/PD-69-132.

Twelve isolates of Diaporthe phaseolorum var. caulivora that cause stem canker disease of soybeans (Glycine max) were compared for their relative virulence on field-grown plants of the soybean cultivars Tracy, Bragg, and J77-339. A wide range of virulence was measured among isolates. The most virulent caused lesions with a mean length up to 61.9 cm at 60 days after inoculation; the least virulent caused lesions averaging 20.7 cm at 60 days. Differences in virulence of the pathogen are believed to contribute to observed variation in severity of the disease at different locations. Fifteen soybean cultivars resistant to stem canker disease were identified.