Tuesday, November 14, 2006 - 2:15 PM

Identifying Soybean Varieties with Yield Potential and Genetic Stability.

Jason L. De Bruin and Palle Pedersen. Iowa State University, 2104 Agronomy Hall, Ames, IA 50011-1010

Variety selection is the most critical step in achieving high yields. Variation in soil type, rainfall and soilborne pathogens increases the challenge of selecting a variety that has both high yield potential and low genotype by environment interaction to minimize risk. Soil fumigation was used to modify the soil pathogen populations and varieties were then evaluated in fumigated and non-fumigated conditions to determine characteristics that contribute to yield and environment stability. The experimental design was a randomized complete block in a split-plot arrangement with four replications and was conducted for three years at three locations in Iowa. Main plot was soil fumigation and the split plot was different soybean varieties. Main effect and interaction responses with soil fumigation were not significant even though pathogen populations, including soybean cyst nematode (SCN), were reduced relative to non-fumigated treatments. Modern varieties produced yields 1.4 Mg ha-1 greater than varieties released between 1927 and 1951 due to breeding improvements. There was no yield difference between modern conventional, including private and public varieties, and glyphosate resistant varieties. The top five yielding varieties across six environments were resistant to SCN and increased yield 0.26 to 0.67 Mg ha-1 and had greater yield stability compared to susceptible varieties, even at locations with low SCN populations. Based on these data modern varieties have greater yield potential than earlier released varieties and SCN resistance is important for unlocking more of that yield potential and maintaining stability across environments. Our recommendations for Iowa growers are to place more emphasis on selecting varieties that match their field conditions and when SCN has been identified that resistant varieties are selected.