The narrow genetic base of the U.S. cultivated soybean has been a concern to soybean growers and producers in terms of how the crop will respond to pest outbreaks that may overcome the genetic resistance commonly used in breeding cultivars. Concurrent to this concern is the fact that soybean cyst nematode (SCN) is one of the most destructive and yield- damaging pest to which soybean may be exposed. Once the nematode is in the soil it cannot be eradicated; it is in the soil forever. Since nematode populations are genetically variable, new types that could overcome resistance may arise under environmentally favorable circumstances. Cultivars with genetic resistance are the only feasible...