1. Institute of Crop Science and Resource Conservation, Crop Functional Genomics, University of Bonn , 53113 Bonn, Germany
2. Department of Statistics, Iowa State University , Ames, Iowa 50011-1210, USA
3. Institute of Crop Science and Resource Conservation, Crop Bioinformatics, University of Bonn , 53115 Bonn, Germany
4. Emmy Noether Group Root Functional Biology, Institute of Crop Science and Resource Conservation, University of Bonn , 53113 Bonn, Germany
5. Institute of Crop Science, Biostatistics Unit, University of Hohenheim , 70599 Stuttgart, Germany