A Selective Toxin produced by Periconia circinata

Abstract

TOXINS with species and varietal specificity have often been postulated, but so far only one such substance has been isolated from a plant pathogen¹. Helminthosporium victoriae, causal agent of a blight of certain oat cultivars, produces an extremely powerful exotoxin which has the same specificity for plants as does the fungus itself. Thus, the Helminthosporium blight is a valuable model for study of the biochemistry of disease. However, there are difficulties; most strains of the fungus give low yields of toxin in vitro, and the compound is very unstable². Isolation of other selective toxins might overcome such difficulties and should indicate whether or not specific toxins are commonly involved in plant diseases. A second selective toxin which shows promise for further study has now been found.