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Physiology and Biochemistry

Association of Formamide Hydro-lyase with Fungal Pathogenicity to Cyanogenic Plants. W. E. Fry, Department of Plant Pathology, Cornell University, Ithaca, NY 14853; P. H. Evans, Department of Plant Pathology, Cornell University, Ithaca, NY 14853. Phytopathology 67:1001-1006. Accepted for publication 17 February 1977. Copyright © 1977 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-67-1001.

To estimate the occurrence of formamide hydro-lyase (FHL) among fungi, 31 species of fungi were tested for FHL. Induction by low levels (1.0 mM) of HCN generally caused at least a 50-fold increase in detectable activity. Formamide hydro-lyase was produced by one of six fungi not pathogenic to plants, nine of fourteen pathogens of non-cyanogenic plants, and all eleven pathogens of cyanogenic plants. Thus each of these pathogens of cyanogenic plants had a means of detoxifying HCN through conversion to formamide. Large differences in FHL-specific activities in cell-free homogenates were detected among pathogens of cyanogenic plants (4-66 μmoles/min/mg protein) and among pathogens of non-cyanogenic plants (0-72 μmoles/min/mg protein). The mean specific activities for pathogens of cyanogenic plants, pathogens of non-cyanogenic plants, and non-plant pathogens, were 30.1, 7.4, and 0.1 μmoles/min/mg protein, respectively.