1. Agrosystems Research, Wageningen University & Research, 6708 PB Wageningen, The Netherlands
2. Hokkaido Agricultural Research Center, National Agriculture and Food Research Organization, NARO, Niigata 941-0193, Japan
3. Field Crop, Wageningen University & Research, P 430, 8200 AK Lelystad, The Netherlands
4. HLBBV, Kampsweg 27, Wijster, 9418 PD Midden-Drenthe, The Netherlands