VIEW ARTICLE

Involvement of Helminthosporium maydis Race T Toxin During Colonization of Maize Leaves. J. C. Comstock, Postdoctoral Research Associate, Department of Botany and Plant Pathology, Iowa State University, Ames, Iowa 50010, Present address of senior author: Hawaiian Sugar Planters Association, P.O. Box 2450, Honolulu 96804; C. A. Martinson, Department of Botany and Plant Pathology, Iowa State University, Ames, Iowa 50010. Phytopathology 65:616-619. Accepted for publication 9 January 1975. DOI: 10.1094/Phyto-65-616.

A host-specific toxin (Hm-t) produced by Helminthosporium maydis race T aided the establishment of Helminthosporium sp. on maize leaves containing Texas male-sterile cytoplasm (cms-T). Toxin was detected during the early stages of germination of H. maydis race T conidia. Toxin involvement during colonization was determined by monitoring the electrolyte leakage from maize leaves. When Hm-t toxin was supplied at the time of inoculation to spores of race O of H. maydis and race 1 of H. carbonum, the loss of electrolytes during infection was greater than that induced by either the fungus or toxin alone. Hm-t toxin always caused increased electrolyte leakage from cms-T leaves, but never from normal cytoplasm leaves.