VIEW ARTICLE

Cultural and Inoculation Studies of Septoria nodorum, Cause of Glume Blotch of Wheat. A. L. Scharen, Research Plant Pathologist, Crops Research Division, ARS, USDA, Beltsville, Maryland 20705; J. M. Krupinsky, Agricultural Research Technician, Crops Research Division, ARS, USDA, Beltsville, Maryland 20705. Phytopathology 60:1480-1485. Accepted for publication 5 May 1970. DOI: 10.1094/Phyto-60-1480.

Septoria nodorum, cause of glume blotch of wheat, Triticum aestivum, exhibited cultural variability into the ninth single-spore transfer generation. Mycelial color and growth habit, number and formation of pycnidia and spores, and pathogenicity were prominent variable characters. Groups of cultures that produced abundant pycnidia and spores were selected in five transfer generations. From cultures that had many pycnidia and spores, isolates were selected in three transfer generations that produced no spores. When selection pressures were reversed, cultures were returned to original types with equal ease. Variants obtained from single-spore isolations were used to inoculate wheat lines to evaluate pathogenic variability. None of the isolates gave identical reactions on the test plants. Specific resistance to field populations of S. nodorum is not known among the Triticum spp. We have further documented the extreme variability in both cultural characters and pathogenicity of S. nodorum, and recommend not designating physiological races of this pathogen.