1. National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
2. College of Life Science, Shenyang Normal University, Shenyang 110034, China.
3. Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
4. Biology Department, Campus Box 1137, Washington University, St. Louis, MO 63130, USA.