1. National Maize Improvement Center Beijing Key Laboratory of Crop Genetic Improvement Laboratory of Crop Heterosis and Utilization, Joint International Research Laboratory of Crop Molecular Breeding China Agricultural University No.2 Yuanmingyuan West Rd, Haidian District Beijing 100193 China
2. Department of Agronomy Iowa State University 513 Farm House Ln Ames IA 50011‐1050 USA