Occurrence of Chlorotic Spots on Corn Seedlings Infected with Sphacelotheca reiliana and Their Use in Evaluation of Head Smut Resistance. C. A. Matyac, Department of Plant Pathology, University of Minnesota, St. Paul 55108. T. Kommedahl, Department of Plant Pathology, University of Minnesota, St. Paul 55108. Plant Dis. 69:251-254. Accepted for publication 17 September 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-251.

Chlorotic spots containing hyphae develop on the fourth or fifth emerged leaf of corn seedlings infected with Sphacelotheca reiliana. Analysis of data in multidimensional contingency tables showed that symptomatic seedlings are likely to produce sori in inflorescences. Significant rank correlations between greenhouse and field trials indicated that evaluations in the greenhouse using chlorotic spots on seedlings as an indicator of infection aid in predicting relative genotypic differences in smut resistance in the field. Greenhouse tests should include 50 plants for inbreds and 100 plants for hybrids and be grown at 22C, allowing soil to dry to –1.5 bar before resaturation.

Keyword(s): chlorotic fleck, head smut.