Impact of Planting 'Bell', a Soybean Cultivar Resistant to Heterodera glycines,in Wisconsin

Although the soybean cyst nematode (SCN), Heterodera glycines, has been known to exist in Wisconsin for at least 14 years, relatively few growers sample for SCN or use host resistance as a means to manage this nematode. The benefit of planting the SCN-resistant cultivar Bell on a sandy soil in Wisconsin was evaluated in 1992 and 1993. A range of SCN population densities was achieved by planting 11 crops with varying degrees of susceptibility for 1 or 2 years before the evaluation. Averaged over nematode population densities, yield of 'Bell' was 30 to 43% greater than that of the susceptible cuhivars, 'Corsoy 79' and 'BSR 101'. Counts of cysts collected the fall preceding soybean were more predictive of yield than counts taken at planting. Yields of all three cultivars were negatively related (P < 0.001) to cyst populations. Fewer (P < 0.01) eggs were produced on 'Bell' than on the susceptible cuhivars. The annual (fall to fall) change in cyst population densities was dependent on initial nematode density for all cuhivars in 1992 and for the susceptible cultivars in 1993. Yield reductions induced by the SCN under the conditions of this study indicate that planting a SCN-resistant cultivar in Wisconsin can be beneficial if any cysts are detected. The soybean cyst nematode (SCN), Het- erodera glycines Ichinohe, is distributed throughout the north central region of the United States and causes more yield reduc- tion of soybean (Glycine max (L.) Merr.) in the region than any other disease (3). In- festations of SCN were first reported in the 1950s for Missouri and Illinois, in the 1960s for Indiana, in the 1970s for Iowa and Minnesota, and in the 1980s for Kan- sas, Nebraska, Ohio, Michigan, and Wis- consin (15). The estimated number of in- fested fields has increased in the region during the past 5 years (13,18), but the in- cidence of SCN still varies widely among states. For example, in Missouri all but one country with significant soybean produc- tion is known to be infested with SCN (15), whereas the currently recognized inci- dence of SCN in Wisconsin is limited to about 110 fields in 13 counties (Norgren, per. comm.). The impact of SCN on yield of soybean was studied in several states in the north