1. State Key Laboratory of Crop Genetics and Germplasm Enhancement, Key Laboratory of Biology and Germplasm Enhancement of Horticultural Crops in East China Ministry of Agriculture, College of Horticulture, Nanjing Agricultural University Nanjing 210095 China
2. Department of Horticultural Science North Carolina State University Raleigh North Carolina 27607 USA
3. Department of Biology University of Washington Seattle Washington 98195‐1800 USA