Soybean cyst nematode (SeN), Heterodera glycines, is a widespread pest of soybeans in Iowa. The nematode is estimated to be present in three out of every four fields in Iowa (Workneh et al., 1999). The nematode is a serious threat to soybean production because it reproduces very quickly, survives in the soil for many years in the absence of a soybean crop, and can cause substantial yield losses, particularly in dry years. Resistance is a very effective strategy for managing SeN, producing acceptable yields yet suppressing reproduction of the nematode. The number of soybean varieties with genetic resistance to SeN available in maturity groups I, II, and III has increased dramatically since the early 1990s (Figure 1). Today, most soybean seed companies have SeN-resistant soybean varieties available for Iowa growers (Tylka, 2004).