National Engineering Laboratory for Tree Breeding, Key Laboratory for Genetics and Breeding in Forest Trees and Ornamental Plants of Ministry of Education, Tree and Ornamental Plant Breeding and Biotechnology Laboratory of State Forestry Administration, College of Biological Sciences and Biotechnology, Beijing Forestry University, Beijing 100083, P. R. China;
College of Horticulture Science and Technology, Hebei Normal University of Science & Technology, Qinhuangdao 066004, P. R. China;
Research Institute of Forestry of Shanxi Province, Taiyuan 030002, P. R. China;
Department of Chemistry, Guizhou Normal College, Guiyang 550018, P. R. China;
Department of Plant and Soil Science, Texas Tech University, Lubbock, TX, 79409, USA;