Trial results show dual benefits of SCN resistance
The greatest difference in average yields between SCN-resistant and widely grown susceptible varieties in any variety trial location in 2013 was 18.4 bushels per acre (or 56 percent), which occurred at the experiment conducted in a very sandy field near Fruitland, Iowa (figure 1).
Overall, soybean yields were the lowest in the variety trial conducted near Newell, Iowa, in the northwest part of the state. Parts of the experiment were flooded early in the season at that location. Nonetheless, yields of SCN-resistant varieties averaged a little more than 37 bushels per acre, which was 40 percent greater than yields of the average yield of 26.7 bushels per acre for the widely grown susceptible varieties at that experiment (figure 1).
click image to zoomFigure 2. Mean final (end of season) SCN population densities (numbers) of SCN-resistant soybean varieties and widely grown susceptible varieties at trial locations in Iowa in 2013. Data for individual varieties and locations are available at www.isuscntrials.info. Resistant varieties allowed much less SCN reproduction
Initial SCN egg population densities at planting for the nine variety trial locations in 2013 ranged from 431 to 10,952 eggs per 100 cubic centimeters (cc) of soil, which is a little less than a half cup of soil. This was an unusually wide range of initial SCN population densities among the variety trial locations. The final or end-of-season SCN egg population densities under the SCN-resistant varieties were one-fifteenth to one-half of the densities that developed under the widely grown susceptible varieties (figure 2). The amount of soybean yield loss caused by SCN is directly related to the SCN egg population density, so the nematode control provided by SCN-resistant varieties will pay dividends in the form of higher yields the next time soybeans are grown.
The greatest level of nematode control provided by SCN-resistant varieties was at the variety trial near Urbana in 2013 (figure 2). The average SCN population density in the field before the experiment was planted was 431 eggs per 100 cc of soil. At harvest, SCN population densities in this experiment increased to 1,120 eggs per 100 cc of soil under the SCN-resistant varieties. In contrast, the end-of-season SCN population density under the widely grown susceptible varieties in that experiment was 16,350 eggs per 100 cc of soil.
The greatest amount of SCN reproduction on SCN-resistant varieties, as a whole, occurred in the experiment near Leighton in 2013. The field had an initial SCN egg population density of 1,694 eggs per 100 cc of soil; final population densities were 11,745 eggs per 100 cc of soil on average under the SCN-resistant varieties and 28,267 eggs per 100 cc of soil under the widely grown susceptible varieties.
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