1. Department of Agronomy and Natural Resources, Institute of Field and Garden Crops, ARO, the Volcani Center, PO Box 6, Bet Dagan 50 250, Israel;
2. These authors contributed equally to this work
3. Present address: Department of Biology, University of Concordia, 1455 de Maisonneuve Boulevard, West Montreal, Quebec, Canada H3G 1M8;
4. Department of Plant Pathology and Microbiology, Faculty of Agricultural, Food and Environmental Quality Sciences, Hebrew University of Jerusalem, Rehovot 76 100 Israel;