1. College of Horticulture, Beijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, China Agricultural University, Beijing 100193, China
2. Beijing Key Lab of Vegetable Germplasm Improvement, Beijing Vegetable Research Center, Beijing Academy of Agriculture and Forestry Science, Beijing 100097, China
3. School of Agriculture, Virginia State University, PO Box 9061, Petersburg, VA 23806, USA