1. National Engineering Laboratory for Tree Breeding College of Biological Sciences and Technology Beijing Forestry University No. 35 Qinghua East Road Beijing 100083 China
2. Key Laboratory of Genetics and Breeding in Forest Trees and Ornamental Plants Ministry of Education College of Biological Sciences and Technology Beijing Forestry University No. 35 Qinghua East Road Beijing 100083 China
3. Department of Forestry North Carolina State University Raleigh NC 27695‐8203 USA