1. Laboratory of Genetics, Graduate School Experimental Plant Science, Wageningen University, 2 Dreijenlaan 6703 HA Wageningen, The Netherlands (L.B., C.A.-B., M.K.);
2. Laboratory of Plant Physiology, Graduate School Experimental Plant Science, Wageningen University, 6703 BD Wageningen, The Netherlands (D.V.); and
3. Plant Research International, Wageningen-University and Research Centre, NL–6700 AA Wageningen, The Netherlands (K.T., S.P.C.G.)