Author Contributions
Lin Huang and Yufei Feng made contributions to conception and design. Yinyu Zhao and Nan Guo helped with the acquisition of data. Boyu Liu and Lei Hu performed the extraction of genomic DNA and genotyping. Xu Hao performed the statistical analysis, interpreted the data and wrote the manuscript. Yinyu Zhao drew the figures and tables. Nan Guo helped to revise the manuscript. Fang Liu provided guidance on statistical analysis. Xiaoyan Nie and Feng Yu were involved in revising it critically for important intellectual content. All authors gave final approval of the version to be published.