1. School of Agriculture and Biology, Shanghai Jiaotong University, Shanghai 200240, China
2. Institute of Vegetables and Flowers, Chinese Academy of Agriculture Sciences, Beijing 100081, China
3. Hunan Vegetable Research Institute, Hunan Academy of Agriculture Sciences, Changsha 410125, China
4. School of Horticulture, Shenyang Agriculture University, Shenyang 110161, China and
5. Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China