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Association of Cyanide with Infection of Birdsfoot Trefoil by Stemphylium loti. R. L. Millar, Professor, Department of Plant Pathology, Cornell University, Ithaca, New York 14850; Verna J. Higgins, Graduate Assistant, Department of Plant Pathology, Cornell University, Ithaca, New York 14850. Phytopathology 60:104-110. Accepted for publication 11 August 1969. DOI: 10.1094/Phyto-60-104.

Cyanide was released from excised shoots and leaves of birdsfoot trefoil plants infected with Stemphylium loti regardless of whether they were cyanogenic (containing both cyanogenic substrate and beta-glucosidase) or not cyanogenic (containing substrate but lacking beta-glucosidase). Enzymes elaborated by the pathogen in vivo effected the release of HCN from plants not cyanogenic, and presumably acted together with enzymes of host origin in liberating HCN from cyanogenic plants. Infection by S. loti resulted in a degradation of host cyanogenic glucoside, and symptom severity was correlated with the amount of HCN released. S. loti was markedly more tolerant of HCN than were eight other fungi tested. All of eleven fungi when grown on autoclaved trefoil shoots or leaves produced enzymes that were effective in releasing HCN from trefoil cyanogenic substrate or from amygdalin.