VIEW ARTICLE

Host Specificity of a Toxin from Phyllosticta maydis for Texas Cytoplasmically Male-Sterile Maize. J. C. Comstock, Post-Doctoral Research Associate, Department of Botany and Plant Pathology, Iowa State University, Ames 50010; C. A. Martinson(2), and B. G. Gengenbach(3). (2)Associate Professor, Department of Botany and Plant Pathology, Iowa State University, Ames 50010; (3)Former Post-Doctoral Research Associate, Department of Agronomy, University of Illinois, Urbana, Present address: Assistant Professor, Department of Agronomy and Plant Genetics, University of Minnesota, St. Paul 55101. Phytopathology 63:1357-1361. Accepted for publication 23 April 1973. DOI: 10.1094/Phyto-63-1357.

Phyllosticta maydis produced, in culture, a host-specific toxin that caused plant responses similar to those caused by Helminthosporium maydis race T toxin. P. maydis toxin selectively inhibited seedling root growth, induced leaf chlorosis, and caused an increased leakage of electrolytes from maize leaves containing Texas male sterile cytoplasm (Tcms). Toxin treatment of mitochondria isolated from Tcms maize caused an immediate irreversible swelling, uncoupled oxidative phosphorylation, and (depending upon the substrate) either stimulated or inhibited O₂ uptake. The toxin did not affect maize with normal cytoplasm except at very high toxin concentrations.