1. National Key Laboratory for Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing, 210095, China.
2. Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing, 100081, China.
3. Corresponding author. Phone: +86-25-84396516. Fax: +86-25-84396516. E-mail: wanjm@njau.edu.cn