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Resistance

Criteria for Evaluation of Resistance to Maize Anthracnose. R. L. Nicholson, Assistant Professor, Agricultural Research Service, U.S. Department of Agriculture, Department of Botany and Plant Pathology, Purdue University, W. Lafayette, IN 47907; H. L. Warren, Research Plant Pathologist, Agricultural Research Service, U.S. Department of Agriculture, Department of Botany and Plant Pathology, Purdue University, W. Lafayette, IN 47907. Phytopathology 66:86-90. Accepted for publication 7 July 1975. DOI: 10.1094/Phyto-66-86.

Criteria were determined for the evaluation of susceptible, resistant, and hypersensitively resistant leaf reactions to Colletotrichum graminicola based on characteristics of individual lesions under greenhouse conditions. These lesion types are defined. Neither lesion size nor the extent of leaf tissue affected was judged an adequate independent measure of host reaction. Three isolates of C. graminicola of different geographic origin were tested against each of 183 corn inbreds. The results demonstrated that differential resistance and susceptibility to C. graminicola isolates is common for individual corn genotypes, and suggest the natural occurrence of physiologic races of the pathogen.