1. Institute of Horticultural Production Systems; Leibniz Universität Hannover; Herrenhäuser Straße 2 30419 Hannover Germany
2. KWS Saat AG; Grimsehlstr. 31 37555 Einbeck Germany
3. Department of Plant Breeding; Justus-Liebig-University Giessen; Heinrich-Buff Ring 26-32 35392 Giessen Germany
4. Department of Agronomy; University of Rostock; Justus-von-Liebig-Weg 6 18059 Rostock Germany