Effect of Four Years of Continuous Cropping of Maturity Group II Soybeans Resistant to Brown Stem Rot on Brown Stem Rot and Yield. H. Tachibana, Research Plant Pathologist, USDA-ARS, and Adjunct Professor, Department of Plant Pathology, Iowa State University, Ames 50011. A. H. Epstein, and B. J. Havlovic. Professor, Department of Plant Pathology, Iowa State University, Ames 50011, and Superintendent, Southeast Research Center, Crawfordsville, IA 52621. Plant Dis. 73:846-849. Accepted for publication 3 May 1989. 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, 1989. DOI: 10.1094/PD-73-0846.

Incidence and severity of brown stem rot (BSR) of soybeans were progressively reduced by long-term cropping with the maturity group II BSR-resistant A3 germ plasm line. BSR incidence remained high and severity fluctuated with long-term cropping of the BSR-susceptible cultivar Coles. Yield increases averaged 16.7% greater for four susceptible cultivars that were grown after the land had been cropped for 4 yr with the BSR-resistant A3 germ plasm than for land that had been cropped with the BSR-susceptible cultivar Coles. Average yields for four BSR-resistant lines also increased with cropping of the BSR-resistant soybean, but the yield increases were smaller (8.3%).