1Dept of Biolgical Science and Technology, School of Life Sci, Nanjing Univ, Nanjing 210093; 2Yueyang Inst of Agri Sci, Yueyang 414109; 3Shanghai Key Lab of Agri Genetics and Breeding, Agro-biotechnology Res Center, Shanghai Acad of Agri Sci; Shanghai 201106; China