1. College of Tropical Crops, Hainan University, Haikou 570228, P. R. China
2. Key Laboratory of Jiangsu Province for Agrobiology, Institute of Germplasm Resources and Biotechnology, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, P. R. China
3. Zhongshan Biological Breeding Laboratory, Nanjing 210014, P. R. China