Responses of Soybeans and Soybean Cyst Nematodes to Cropping Sequences. L. D. Young, Agricultural Research Service, U.S. Department of Agriculture, West Tennessee Experiment Station, Jackson 38301. E. E. Hartwig, USDA-ARS, P.O. Box 196, Stoneville, MS 38776; S. C. Anand, University of Missouri Delta Center, P.O. Box 160, Portageville 63873; and D. Widick, Arkansas State University, P.O. Box 2340, State University 72467. Plant Dis. 70:787-791. Accepted for publication 29 January 1986. 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, 1986. DOI: 10.1094/PD-70-787.

Nine cropping treatments were compared in fields infested with soybean cyst nematodes (SCN) in Arkansas, Missouri, and Tennessee for 6 yr. Seven continuous-culture treatments were six race 3-resistant soybean lines with varying levels of resistance to race 4 (including resistant Bedford and susceptible Forrest) and a 70:30 Bedford/Forrest blend. Two rotations, Bedford with nonhost crop and Bedford with Forrest and SCN-susceptible Essex, were included. At the three locations, there was a trend for more SCN reproduction on race 4-resistant cultivars relative to susceptible cultivars after the resistant cultivars were grown for 4–6 yr. However, cyst densities did not significantly increase, and seed yields of continuously grown resistant cultivars were not significantly different from those of resistant cultivars in alternative cropping treatments. At the Arkansas and Missouri locations, seed yields of the susceptible and resistant cultivars were not significantly different. In Tennessee, mean seed yield for 6 yr of continuous Bedford was 515 kg/ha greater than for continuous Forrest. Cyst densities in soil of continuous Forrest plots were about 2.5 times those in continuous Bedford plots. At all locations, no treatment was superior to continuous Bedford in seed yield.

Keyword(s): Glycine max, Heterodera glycines, rotations.