Analogs of host-specific phytotoxin produced by Helminthosporium maydis, race T : II. Biological activities

Abstract

Inhibition of dark CO 2 fixation by susceptible corn leaves was used to compare the relative toxicity of synthetic analogs with that of the host-specific phytotoxin produced by the fungal corn pathogen, Helminthosporium maydis, race T. Analogs with C 15, C 25, or C 26 chain lengths and 1,5-dioxo-3-hydroxy functions were only slightly less toxic (2–6 × 10 −7 M) than native T toxin (C 35–C 45 chain lengths) or its individual components (3 × 10 −8 M). Like native toxin, analogs were host-specific in that they did not inhibit dark CO 2 fixation in leaf tissue of resistant corn at concentrations 10 2–10 3 times greater than those effective with susceptible corn. These findings support the structures previously proposed for native T toxin.