1. Eastern Cereal and Oilseed Research Centre, Agriculture and Agri-Food Canada, Ottawa, Ontario, K1A 0C6 Canada
2. Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, and Northern Forestry Centre, Canadian Forest Service, Edmonton, Alberta, T6H 3S5 Canada
3. Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada