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Identification of the Self-Inhibitor and Some Germination Characteristics of Peanut Rust Uredospores. A. S. Foudin, Boyce Thompson Institute, Yonkers, New York 10701, Present address of senior author: Graduate student in the Department of Plant Pathology and Plant Genetics, University of Georgia, Athens 30602; V. Macko, Boyce Thompson Institute, Yonkers, New York 10701. Phytopathology 64:990-993. Accepted for publication 14 February 1974. DOI: 10.1094/Phyto-64-990.

The native germination self-inhibitor of Puccinia arachidis uredospores has been identified as methyl cis-3,4-dimethoxycinnamate. Uredospores of the peanut rust fungus were more sensitive to the self-inhibitor than any other rust whose self-inhibitor has been identified (ED₅₀ = 8 picograms per milliliter). During germination, peanut rust uredospores, as is typical of uredospores having the dimethoxycinnamate self-inhibitor, required collodion-paraffin oil membranes for induction of infection structures, while heat-shock treatments were ineffective. Freezing the spores in liquid nitrogen did not induce cold-dormancy, and a brief exposure to heat was unnecessary to initiate germination.