1. State Key Laboratory of Grassland Agro-ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou, Gansu Province 730020, China
2. Forage Improvement Division, the Samuel Roberts Noble Foundation, Ardmore, Oklahoma 73401-2124
3. NARO Tohoku Agricultural Research Center, Morioka, Iwate 020-0198, Japan
4. Institute of Integrative Biology, ETH Zürich, CH-8092 Zürich, Switzerland
5. Department of Plant Pathology, University of Kentucky, Lexington, Kentucky 40546-0312