1. Department of Applied Microbiology and Food Science, University of Saskatchewan, 51 Campus Drive, Saskatoon, SK, S7N 5A8 Canada.
2. Corresponding author. Phone: 306/966-5008. Fax: 306/966-8898. E-mail: zhengg@skyfox.usask.ca
3. Crop Development Centre, University of Saskatchewan, 51 Campus Drive, Saskatoon, SK, S7N 5A8 Canada.