1. Department of Plant Pathology, Cornell University, 334 Plant Science Building, Ithaca, New York 14853
2. National Center for Biotechnology Information, National Institutes of Health, Bethesda, Maryland 20894
3. CABI Bioscience UK Centre (Ascot), Silwood Park, Buckhurst Road, Ascot, BERKS. SL5 7TA, U. K.