Race of Helminthosporium turcicum Not Controlled by Ht Genetic Resistance in Corn in the American Corn Belt. M. T. Turner, Research Scientist, Funk Seeds International, Bloomington, IL 61701. E. R. Johnson, Senior Research Assistant, Funk Seeds International, Bloomington, IL 61701. Plant Dis. 64:216-217. Accepted for publication 25 October 1979. Copyright 1980 American Phytopathological Society. DOI: 10.1094/PD-64-216.

A race of Helminthosporium turcicum capable of overcoming the Ht monogenic resistance in Zea mays has been found in inbreds and hybrids near Brook, Indiana. The resistant chlorotic lesions conditioned by the Ht gene as a response to infection by the common U.S. race of H. turcicum now appear as completely susceptible lesions as a response to infection by this newly found race. Comparisons of several sources of the Ht gene and several isolates of the pathogen indicate race differences. On NN14B lesions were resistant with both old and new races.