Cultivar Resistance to Field Infestations of Soybean Stem Canker. D. B. Weaver, Assistant Professor, Department of Agronomy and Soils, Alabama Agricultural Experiment Station, Auburn University 36849. B. H. Cosper, Research Associate, Department of Agronomy and Soils, and P. A. Backman, Professor, and M. A. Crawford, Research Associate, Department of Botany, Plant Pathology, and Microbiology, Alabama Agricultural Experiment Station, Auburn University 36849.. Plant Dis. 68:877-879. Accepted for publication 13 April 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/PD-68-877.

Forty-one adapted soybean cultivars were evaluated for resistance to stem canker caused by Diaporthe phaseolorum var. caulivora in naturally infested fields, and effects of the disease on seed yield were determined. In 2 yr of field evaluations, almost all adapted soybean cultivars were susceptible to stem canker. Disease expression among cultivars varied from highly resistant to highly susceptible, with most cultivars between these extremes. Braxton and Tracy-M were virtually immune, whereas Hutton, Coker 237, and other cultivars were highly susceptible. Seed yield was negatively correlated with disease severity in all environments.

Keyword(s): genetic resistance, Glycine max.