1. Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture, College of Animal Sciences and Technology, China Agricultural University, Beijing 100094, P. R. China
2. Sichuan Key Laboratory of Conservation and Utilization of Animal Genetic Resources in Tibetan Plateau, Southwest University for Nationalities, Chengdu City 610041, P. R. China
3. State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, P. R. China