Physiological Races of Colletotrichum graminicola on Sorghum. M. E. K. Ali, Graduate Research Assistant, USDA, ARS, Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907. H. L. Warren, Professor of Plant Pathology and Research Plant Pathologist, USDA, ARS, Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907. Plant Dis. 71:402-404. Accepted for publication 13 November 1986. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1987. DOI: 10.1094/PD-71-0402.

Nine sorghum isolates of Colletotrichum graminicola from different geographical areas were tested for pathogenicity on six sorghum lines in the greenhouse and at the Purdue Agronomy Farm. Sorghum lines were evaluated for reaction type and disease severity. Similar results were obtained from both field and greenhouse studies, except leaf anthracnose severity was higher in the field than in the greenhouse. Sorghum lines IS4225 and IS8361 were susceptible, whereas Br64 and 954206 were resistant to all isolates. Based on the differential responses of sorghum lines 954130 and 954062, the isolates were grouped into three physiological races designated 1, 2, and 3. These findings suggest that a resistant sorghum cultivar in one region may succumb to leaf anthracnose in another region because of the prevalence of a different virulent race.

Keyword(s): anthracnose, Sorghum bicolor.