Introduction

The soybean, Glycine max (L.) Merr., is one of numerous domesticated plants used as human food. It is a major crop in the United States, Brazil, China and Argentina and important in many other countries. Currently world production of soybean is greater than any other oilseed crop. It has only

Department of Agronomy and Plant Genetics, University of Minnesota, 411 Borlaug Hall, 1991 Upper Buford Circle, St. Paul, MN 55108-6026, USA; e-mail: orfxx001@umn.edu

been since the 1960s that soybean emerged as the dominant oilseed crop produced (Smith and Huyser 1987). Demand for soybean continued and still is continuing to grow on a worldwide basis (Wilcox 2004; Goldsmith 2008; Orf 2008).