1. Norwegian Institute for Agricultural and Environmental Research; Arable Crops Division; 2849 Kapp Norway
2. Dep. of Plant Sciences, 51 Campus Dr., College of Agriculture and Bioresources; Univ. of Saskatchewan; Saskatoon SK Canada
3. Dep. of Plant and Environmental Sciences; Norwegian Univ. of Life Sciences; P.O Box 5003 1432 Ås Norway