1. Institute of Applied Biotechnology, University of Kuopio, P.O. Box 1627, FI-70211 Kuopio, Finland; MTT Agrifood Research Finland, Horticulture, Toivonlinnantie 518, FI-21500 Piikkiö, Finland; The Norwegian Crop Research Institute, Kvithamar Research Centre, N-7500 Stjørdal, Norway; The Norwegian Crop Research Institute, Særheim Research Centre, N-4353 Klepp st., Norway; and MTT Agrifood Research Finland, FI-31600 Jokioinen, Finland