Multiple Polyploidy Events in the Early Radiation of Nodulating and Nonnodulating Legumes Steven B. Cannon,*,y,1 Michael R. McKain,y,2,3 Alex Harkess,y,2 Matthew N. Nelson,4,5 Sudhansu Dash,6 Michael K. Deyholos,7 Yanhui Peng,8 Blake Joyce,8 Charles N. Stewart Jr,8 Megan Rolf,3 Toni Kutchan,3 Xuemei Tan,9 Cui Chen,9 Yong Zhang,9 Eric Carpenter,7 Gane Ka-Shu Wong,7,9,10 Jeff J. Doyle,11 and Jim Leebens-Mack2 1USDA-Agricultural Research Service, Corn Insects and Crop Genetics Research Unit, Ames, IA 2Department of Plant Biology, University of Georgia 3Donald Danforth Plant Sciences Center, St Louis, MO 4The UWA Institute of Agriculture, The University of Western Australia, Crawley, WA, Australia 5The School of Plant Biology, The University of Western Australia, Crawley, WA, Australia 6Virtual Reality Application Center, Iowa State University 7Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada 8Department of Plant Sciences, The University of Tennessee Downloaded from 9BGI-Shenzhen, Bei Shan Industrial Zone, Shenzhen, China 10Department of Medicine, University of Alberta, Edmonton, AB, Canada 11L. H. Bailey Hortorium, Department of Plant Biology, Cornell University yThese authors contributed equally to this work. *Corresponding author: E-mail:
[email protected]. http://mbe.oxfordjournals.org/ Associate editor:BrandonGaut Abstract Unresolved questions about evolution of the large and diverselegumefamilyincludethetiming of polyploidy (whole- genome duplication; WGDs) relative to the origin of the major lineages within the Fabaceae and to the origin of symbiotic nitrogen fixation. Previous work has established that a WGD affects most lineages in the Papilionoideae and occurred sometime after the divergence of the papilionoid and mimosoid clades, but the exact timing has been unknown.