1. Dep. of Plant Science, Horticulture Research Centre; Univ. Laval; Québec QC G1V 0A6 Canada
2. Agriculture and Agri-Food Canada, Horticulture Research Centre; Univ. Laval; Québec QC G1V 0A6 Canada
3. Dep. of Horticulture, Microbial Horticulture Lab.; Swedish Univ. of Agricultural Sciences; P.O. Box 103 Alnarp SE-230 53 Sweden
4. Dep. of Civil, Geological and Mining Engineering, École Polytechnique de Montréal; Montreal QC H3C 3A7 Canada