Abstract
Tylka, G.L., and S. K. Souhrada. 1997. Yield losses of Heterodera glycines-resistant soybean cultivars in Iowa in 1996. Journal of Nematology 29: (in press).
Resistant soybean cultivars are used by Iowa soybean growers to manage the soybean cyst nematode, Heterodera glycines. Experiments are conducted each year to evaluate the agronomic performance of maturity group (MG) I, II, and III, H. glycines-resistant soybean cultivars in H. glycines-infested and nearby noninfested fields in north central, central, and south east Iowa. Several susceptible cultivars of each MG also are included in the experiments. In 1996, average yields of the resistant soybean cultivars, combined by MG, were 16.6% to 44.2% greater than those of susceptible cultivars of the same MG in H. glycines-infested fields. However, yields of the resistant cultivars averaged 14.1% to 33.5% greater in the noninfested fields than in the infested fields. Individual resistant cultivar yields were 2.5% to 47.5% greater in noninfested fields than in infested fields, indicating variation in tolerance of the resistant cultivars to the nematode. Resistant soybean cultivars consistently yield less in H. glycines-infested fields than in nearby noninfested fields in Iowa, which emphasizes the need for integrated management of this pest.