1. Department of Vegetable Science, College of Horticulture, China Agricultural University , Beijing 100193 , China
2. Agricultural and Rural Bureau of Qingxian in Hebei Province , Qingxian 062650 , China
3. USDA-ARS, Vegetable Crops Research Unit, Horticulture Department, University of Wisconsin , Madison, WI 53706 , USA
4. Sanya Institute of China Agricultural University , Sanya 572019 , China
5. Engineering Research Center of Breeding and Propagation of Horticultural Crops, Ministry on Education, College of Horticulture, China Agricultural University , Beijing 100193 , China