1. Departments of Crop Sciences and Microbiology, University of Illinois at Urbana-Champaign, 240 ERML, 1201 West Gregory Drive, Urbana, IL 61801, USA
2. Soybean Genomics and Improvement Laboratory, Plant Sciences Institute, USDA-ARS, Beltsville, MD, 20705, USA
3. Laboratoire de Sciences de la Terre, Ecole Normale Superieure de Lyon, 69364 Lyon Cedex 07, France